diff --git a/cypress/e2e/2-credentials.cy.ts b/cypress/e2e/2-credentials.cy.ts
index dbc613bd64..8ce3bc4080 100644
--- a/cypress/e2e/2-credentials.cy.ts
+++ b/cypress/e2e/2-credentials.cy.ts
@@ -15,7 +15,7 @@ import {
 	TRELLO_NODE_NAME,
 } from '../constants';
 import { CredentialsModal, CredentialsPage, NDV, WorkflowPage } from '../pages';
-import { successToast } from '../pages/notifications';
+import { errorToast, successToast } from '../pages/notifications';
 import { getVisibleSelect } from '../utils';
 
 const credentialsPage = new CredentialsPage();
@@ -278,4 +278,25 @@ describe('Credentials', () => {
 		credentialsModal.getters.credentialAuthTypeRadioButtons().first().click();
 		nodeDetailsView.getters.copyInput().should('not.exist');
 	});
+
+	it('ADO-2583 should show notifications above credential modal overlay', () => {
+		// check error notifications because they are sticky
+		cy.intercept('POST', '/rest/credentials', { forceNetworkError: true });
+		credentialsPage.getters.createCredentialButton().click();
+
+		credentialsModal.getters.newCredentialModal().should('be.visible');
+		credentialsModal.getters.newCredentialTypeSelect().should('be.visible');
+		credentialsModal.getters.newCredentialTypeOption('Notion API').click();
+
+		credentialsModal.getters.newCredentialTypeButton().click();
+		credentialsModal.getters.connectionParameter('Internal Integration Secret').type('1234567890');
+
+		credentialsModal.actions.setName('My awesome Notion account');
+		credentialsModal.getters.saveButton().click({ force: true });
+		errorToast().should('have.length', 1);
+		errorToast().should('be.visible');
+
+		errorToast().should('have.css', 'z-index', '2100');
+		cy.get('.el-overlay').should('have.css', 'z-index', '2001');
+	});
 });
diff --git a/packages/editor-ui/src/App.vue b/packages/editor-ui/src/App.vue
index 4c849fb5d9..77d371855c 100644
--- a/packages/editor-ui/src/App.vue
+++ b/packages/editor-ui/src/App.vue
@@ -16,6 +16,7 @@ import { useUIStore } from '@/stores/ui.store';
 import { useUsersStore } from '@/stores/users.store';
 import { useSettingsStore } from '@/stores/settings.store';
 import { useHistoryHelper } from '@/composables/useHistoryHelper';
+import { useStyles } from './composables/useStyles';
 
 const route = useRoute();
 const rootStore = useRootStore();
@@ -24,6 +25,8 @@ const uiStore = useUIStore();
 const usersStore = useUsersStore();
 const settingsStore = useSettingsStore();
 
+const { setAppZIndexes } = useStyles();
+
 // Initialize undo/redo
 useHistoryHelper(route);
 
@@ -41,6 +44,7 @@ watch(defaultLocale, (newLocale) => {
 });
 
 onMounted(async () => {
+	setAppZIndexes();
 	logHiringBanner();
 	void useExternalHooks().run('app.mount');
 	loading.value = false;
@@ -134,7 +138,7 @@ const updateGridWidth = async () => {
 
 .banners {
 	grid-area: banners;
-	z-index: 999;
+	z-index: var(--z-index-top-banners);
 }
 
 .content {
@@ -154,13 +158,13 @@ const updateGridWidth = async () => {
 
 .header {
 	grid-area: header;
-	z-index: 99;
+	z-index: var(--z-index-app-header);
 }
 
 .sidebar {
 	grid-area: sidebar;
 	height: 100%;
-	z-index: 999;
+	z-index: var(--z-index-app-sidebar);
 }
 
 .modals {
diff --git a/packages/editor-ui/src/components/AskAssistant/AskAssistantChat.vue b/packages/editor-ui/src/components/AskAssistant/AskAssistantChat.vue
index bef68236f8..db4d8ee105 100644
--- a/packages/editor-ui/src/components/AskAssistant/AskAssistantChat.vue
+++ b/packages/editor-ui/src/components/AskAssistant/AskAssistantChat.vue
@@ -106,7 +106,7 @@ function onClose() {
 .container {
 	height: 100%;
 	flex-basis: content;
-	z-index: 300;
+	z-index: var(--z-index-ask-assistant-chat);
 }
 
 .wrapper {
diff --git a/packages/editor-ui/src/components/AskAssistant/AskAssistantFloatingButton.vue b/packages/editor-ui/src/components/AskAssistant/AskAssistantFloatingButton.vue
index b147ecca9f..70f6ed84fd 100644
--- a/packages/editor-ui/src/components/AskAssistant/AskAssistantFloatingButton.vue
+++ b/packages/editor-ui/src/components/AskAssistant/AskAssistantFloatingButton.vue
@@ -1,5 +1,6 @@
 <script setup lang="ts">
 import { useI18n } from '@/composables/useI18n';
+import { useStyles } from '@/composables/useStyles';
 import { useAssistantStore } from '@/stores/assistant.store';
 import AssistantAvatar from 'n8n-design-system/components/AskAssistantAvatar/AssistantAvatar.vue';
 import AskAssistantButton from 'n8n-design-system/components/AskAssistantButton/AskAssistantButton.vue';
@@ -7,6 +8,7 @@ import { computed } from 'vue';
 
 const assistantStore = useAssistantStore();
 const i18n = useI18n();
+const { APP_Z_INDEXES } = useStyles();
 
 const lastUnread = computed(() => {
 	const msg = assistantStore.lastUnread;
@@ -39,7 +41,7 @@ const onClick = () => {
 		data-test-id="ask-assistant-floating-button"
 	>
 		<n8n-tooltip
-			:z-index="4000"
+			:z-index="APP_Z_INDEXES.ASK_ASSISTANT_FLOATING_BUTTON_TOOLTIP"
 			placement="top"
 			:visible="!!lastUnread"
 			:popper-class="$style.tooltip"
@@ -61,7 +63,7 @@ const onClick = () => {
 	position: absolute;
 	bottom: var(--spacing-s);
 	right: var(--spacing-s);
-	z-index: 3000;
+	z-index: var(--z-index-ask-assistant-floating-button);
 }
 
 .tooltip {
diff --git a/packages/editor-ui/src/components/HoverableNodeIcon.vue b/packages/editor-ui/src/components/HoverableNodeIcon.vue
deleted file mode 100644
index b30894ceb1..0000000000
--- a/packages/editor-ui/src/components/HoverableNodeIcon.vue
+++ /dev/null
@@ -1,184 +0,0 @@
-<script lang="ts">
-import { type StyleValue, defineComponent, type PropType } from 'vue';
-
-import type { ITemplatesNode } from '@/Interface';
-import type { INodeTypeDescription } from 'n8n-workflow';
-import { mapStores } from 'pinia';
-import { useRootStore } from '@/stores/root.store';
-
-interface NodeIconData {
-	type: string;
-	path?: string;
-	icon?: string;
-	fileExtension?: string;
-	fileBuffer?: string;
-}
-
-export default defineComponent({
-	name: 'HoverableNodeIcon',
-	props: {
-		circle: {
-			type: Boolean,
-			default: false,
-		},
-		clickButton: {
-			type: Function,
-		},
-		disabled: {
-			type: Boolean,
-			default: false,
-		},
-		nodeType: {
-			type: Object as PropType<INodeTypeDescription>,
-			required: true,
-		},
-		size: {
-			type: Number,
-		},
-	},
-	computed: {
-		...mapStores(useRootStore),
-		fontStyleData(): object {
-			return {
-				'max-width': this.size + 'px',
-			};
-		},
-		iconStyleData(): StyleValue {
-			const nodeType = this.nodeType;
-			const nodeTypeColor = nodeType?.defaults?.color;
-			const color = typeof nodeTypeColor === 'string' ? nodeTypeColor : '';
-
-			if (!this.size) {
-				return { color };
-			}
-
-			return {
-				color,
-				width: this.size + 'px',
-				height: this.size + 'px',
-				'font-size': this.size + 'px',
-				'line-height': this.size + 'px',
-				'border-radius': this.circle ? '50%' : '2px',
-				...(this.disabled && {
-					color: 'var(--color-text-light)',
-					'-webkit-filter': 'contrast(40%) brightness(1.5) grayscale(100%)',
-					filter: 'contrast(40%) brightness(1.5) grayscale(100%)',
-				}),
-			};
-		},
-		imageStyleData(): StyleValue {
-			return {
-				width: '100%',
-				'max-width': '100%',
-				'max-height': '100%',
-			};
-		},
-		nodeIconData(): null | NodeIconData {
-			const nodeType = this.nodeType as INodeTypeDescription | ITemplatesNode | null;
-			if (nodeType === null) {
-				return null;
-			}
-
-			if ((nodeType as ITemplatesNode).iconData) {
-				return (nodeType as ITemplatesNode).iconData;
-			}
-
-			const restUrl = this.rootStore.restUrl;
-
-			if (typeof nodeType.icon === 'string') {
-				const [type, path] = nodeType.icon.split(':');
-				const returnData: NodeIconData = {
-					type,
-					path,
-				};
-
-				if (type === 'file') {
-					returnData.path = restUrl + '/node-icon/' + nodeType.name;
-					returnData.fileExtension = path.split('.').slice(-1).join();
-				}
-
-				return returnData;
-			}
-			return null;
-		},
-	},
-	data() {
-		return {
-			showTooltip: false,
-		};
-	},
-});
-</script>
-
-<template>
-	<div
-		:class="$style.wrapper"
-		:style="iconStyleData"
-		@click="() => $emit('click')"
-		@mouseover="showTooltip = true"
-		@mouseleave="showTooltip = false"
-	>
-		<div :class="$style.tooltip">
-			<n8n-tooltip placement="top" :visible="showTooltip">
-				<template #content>
-					<div v-text="nodeType.displayName"></div>
-				</template>
-				<span />
-			</n8n-tooltip>
-		</div>
-		<div v-if="nodeIconData !== null" :class="$style.icon" title="">
-			<div :class="$style.iconWrapper" :style="iconStyleData">
-				<div v-if="nodeIconData !== null" :class="$style.icon">
-					<img
-						v-if="nodeIconData.type === 'file'"
-						:src="nodeIconData.fileBuffer || nodeIconData.path"
-						:style="imageStyleData"
-					/>
-					<font-awesome-icon
-						v-else
-						:icon="nodeIconData.icon || nodeIconData.path"
-						:style="fontStyleData"
-					/>
-				</div>
-				<div v-else class="node-icon-placeholder">
-					{{ nodeType !== null ? nodeType.displayName.charAt(0) : '?' }}
-				</div>
-			</div>
-		</div>
-		<div v-else :class="$style.placeholder">
-			{{ nodeType !== null ? nodeType.displayName.charAt(0) : '?' }}
-		</div>
-	</div>
-</template>
-
-<style lang="scss" module>
-.wrapper {
-	cursor: pointer;
-	z-index: 2000;
-}
-
-.icon {
-	height: 100%;
-	width: 100%;
-	display: flex;
-	justify-content: center;
-	align-items: center;
-}
-
-.iconWrapper {
-	svg {
-		height: 100%;
-		width: 100%;
-	}
-}
-
-.placeholder {
-	text-align: center;
-}
-
-.tooltip {
-	left: 10px;
-	position: relative;
-	z-index: 9999;
-}
-</style>
diff --git a/packages/editor-ui/src/components/Modal.vue b/packages/editor-ui/src/components/Modal.vue
index 3877b8dc53..3f98e2a023 100644
--- a/packages/editor-ui/src/components/Modal.vue
+++ b/packages/editor-ui/src/components/Modal.vue
@@ -5,6 +5,7 @@ import type { EventBus } from 'n8n-design-system';
 import { useUIStore } from '@/stores/ui.store';
 import type { ModalKey } from '@/Interface';
 import { APP_MODALS_ELEMENT_ID } from '@/constants';
+import { useStyles } from '@/composables/useStyles';
 
 const props = withDefaults(
 	defineProps<{
@@ -50,6 +51,8 @@ const props = withDefaults(
 
 const emit = defineEmits<{ enter: [] }>();
 
+const { APP_Z_INDEXES } = useStyles();
+
 const styles = computed(() => {
 	const styles: { [prop: string]: string } = {};
 	if (props.height) {
@@ -143,7 +146,7 @@ function getCustomClass() {
 		:append-to-body="appendToBody"
 		:data-test-id="`${name}-modal`"
 		:modal-class="center ? $style.center : ''"
-		:z-index="2000"
+		:z-index="APP_Z_INDEXES.MODALS"
 	>
 		<template v-if="$slots.header" #header>
 			<slot v-if="!loading" name="header" />
diff --git a/packages/editor-ui/src/components/Node/NodeCreator/NodeCreator.vue b/packages/editor-ui/src/components/Node/NodeCreator/NodeCreator.vue
index d93e83ebfa..82767f964d 100644
--- a/packages/editor-ui/src/components/Node/NodeCreator/NodeCreator.vue
+++ b/packages/editor-ui/src/components/Node/NodeCreator/NodeCreator.vue
@@ -173,7 +173,7 @@ onBeforeUnmount(() => {
 	top: $header-height;
 	bottom: 0;
 	right: 0;
-	z-index: 200;
+	z-index: var(--z-index-node-creator);
 	width: $node-creator-width;
 	color: $node-creator-text-color;
 }
diff --git a/packages/editor-ui/src/components/NodeDetailsView.vue b/packages/editor-ui/src/components/NodeDetailsView.vue
index f66800e384..8294ff2f24 100644
--- a/packages/editor-ui/src/components/NodeDetailsView.vue
+++ b/packages/editor-ui/src/components/NodeDetailsView.vue
@@ -36,6 +36,7 @@ import { usePinnedData } from '@/composables/usePinnedData';
 import { useTelemetry } from '@/composables/useTelemetry';
 import { useI18n } from '@/composables/useI18n';
 import { storeToRefs } from 'pinia';
+import { useStyles } from '@/composables/useStyles';
 
 const emit = defineEmits<{
 	saveKeyboardShortcut: [event: KeyboardEvent];
@@ -73,6 +74,7 @@ const deviceSupport = useDeviceSupport();
 const telemetry = useTelemetry();
 const i18n = useI18n();
 const message = useMessage();
+const { APP_Z_INDEXES } = useStyles();
 
 const settingsEventBus = createEventBus();
 const redrawRequired = ref(false);
@@ -668,7 +670,7 @@ onBeforeUnmount(() => {
 		width="auto"
 		:append-to="`#${APP_MODALS_ELEMENT_ID}`"
 		data-test-id="ndv"
-		:z-index="1800"
+		:z-index="APP_Z_INDEXES.NDV"
 		:data-has-output-connection="hasOutputConnection"
 	>
 		<n8n-tooltip
diff --git a/packages/editor-ui/src/components/Sticky.vue b/packages/editor-ui/src/components/Sticky.vue
index 0d11628901..12ee2dfa89 100644
--- a/packages/editor-ui/src/components/Sticky.vue
+++ b/packages/editor-ui/src/components/Sticky.vue
@@ -20,6 +20,7 @@ import { assert } from '@/utils/assert';
 import type { BrowserJsPlumbInstance } from '@jsplumb/browser-ui';
 import { useNodeBase } from '@/composables/useNodeBase';
 import { useTelemetry } from '@/composables/useTelemetry';
+import { useStyles } from '@/composables/useStyles';
 
 const props = withDefaults(
 	defineProps<{
@@ -54,6 +55,7 @@ const ndvStore = useNDVStore();
 const nodeTypesStore = useNodeTypesStore();
 const uiStore = useUIStore();
 const workflowsStore = useWorkflowsStore();
+const { APP_Z_INDEXES } = useStyles();
 
 const isResizing = ref<boolean>(false);
 const isTouchActive = ref<boolean>(false);
@@ -136,7 +138,9 @@ const stickySize = computed<StyleValue>(() => ({
 const stickyPosition = computed<StyleValue>(() => ({
 	left: position.value[0] + 'px',
 	top: position.value[1] + 'px',
-	zIndex: props.isActive ? 9999999 : -1 * Math.floor((height.value * width.value) / 1000),
+	zIndex: props.isActive
+		? APP_Z_INDEXES.ACTIVE_STICKY
+		: -1 * Math.floor((height.value * width.value) / 1000),
 }));
 
 const workflowRunning = computed(() => uiStore.isActionActive.workflowRunning);
diff --git a/packages/editor-ui/src/components/WorkflowPreview.vue b/packages/editor-ui/src/components/WorkflowPreview.vue
index 4f295b924d..ff617499ff 100644
--- a/packages/editor-ui/src/components/WorkflowPreview.vue
+++ b/packages/editor-ui/src/components/WorkflowPreview.vue
@@ -242,7 +242,7 @@ watch(
 	left: 0;
 	height: 100%;
 	width: 100%;
-	z-index: 9999999;
+	z-index: var(--z-index-workflow-preview-ndv);
 }
 
 .spinner {
diff --git a/packages/editor-ui/src/composables/useCanvasMouseSelect.ts b/packages/editor-ui/src/composables/useCanvasMouseSelect.ts
index 6beaf33d60..83c1edbe42 100644
--- a/packages/editor-ui/src/composables/useCanvasMouseSelect.ts
+++ b/packages/editor-ui/src/composables/useCanvasMouseSelect.ts
@@ -7,6 +7,7 @@ import { getMousePosition, getRelativePosition } from '@/utils/nodeViewUtils';
 import { ref, computed } from 'vue';
 import { useCanvasStore } from '@/stores/canvas.store';
 import { useContextMenu } from './useContextMenu';
+import { useStyles } from './useStyles';
 
 interface ExtendedHTMLSpanElement extends HTMLSpanElement {
 	x: number;
@@ -22,6 +23,7 @@ export default function useCanvasMouseSelect() {
 	const canvasStore = useCanvasStore();
 	const workflowsStore = useWorkflowsStore();
 	const { isOpen: isContextMenuOpen } = useContextMenu();
+	const { APP_Z_INDEXES } = useStyles();
 
 	function _setSelectBoxStyle(styles: Record<string, string>) {
 		Object.assign(selectBox.value.style, styles);
@@ -106,7 +108,7 @@ export default function useCanvasMouseSelect() {
 			border: '2px dotted #FF0000',
 			// Positioned absolutely within #node-view. This is consistent with how nodes are positioned.
 			position: 'absolute',
-			zIndex: '100',
+			zIndex: `${APP_Z_INDEXES.SELECT_BOX}`,
 			visibility: 'hidden',
 		});
 
diff --git a/packages/editor-ui/src/composables/useStyles.spec.ts b/packages/editor-ui/src/composables/useStyles.spec.ts
new file mode 100644
index 0000000000..2e27979b3e
--- /dev/null
+++ b/packages/editor-ui/src/composables/useStyles.spec.ts
@@ -0,0 +1,25 @@
+import { useStyles } from './useStyles';
+
+describe('useStyles', () => {
+	it('sets z-index as css variables', () => {
+		vi.spyOn(global.document.documentElement.style, 'setProperty');
+
+		const { setAppZIndexes } = useStyles();
+
+		setAppZIndexes();
+
+		expect(global.document.documentElement.style.setProperty).toHaveBeenNthCalledWith(
+			1,
+			'--z-index-app-header',
+			'99',
+		);
+		expect(global.document.documentElement.style.setProperty).toHaveBeenCalledWith(
+			'--z-index-canvas-add-button',
+			'101',
+		);
+		expect(global.document.documentElement.style.setProperty).toHaveBeenLastCalledWith(
+			'--z-index-workflow-preview-ndv',
+			'9999999',
+		);
+	});
+});
diff --git a/packages/editor-ui/src/composables/useStyles.ts b/packages/editor-ui/src/composables/useStyles.ts
new file mode 100644
index 0000000000..dc1db3ade3
--- /dev/null
+++ b/packages/editor-ui/src/composables/useStyles.ts
@@ -0,0 +1,31 @@
+const APP_Z_INDEXES = {
+	APP_HEADER: 99,
+	SELECT_BOX: 100,
+	CANVAS_ADD_BUTTON: 101,
+	NODE_CREATOR: 200,
+	ASK_ASSISTANT_CHAT: 300,
+	APP_SIDEBAR: 999,
+	CANVAS_SELECT_BOX: 100,
+	TOP_BANNERS: 999,
+	NDV: 1800,
+	MODALS: 2000,
+	TOASTS: 2100,
+	ASK_ASSISTANT_FLOATING_BUTTON: 3000,
+	ASK_ASSISTANT_FLOATING_BUTTON_TOOLTIP: 3000,
+	DRAGGABLE: 9999999,
+	ACTIVE_STICKY: 9999999,
+	WORKFLOW_PREVIEW_NDV: 9999999,
+} as const;
+
+const setAppZIndexes = () => {
+	Object.keys(APP_Z_INDEXES).forEach((key) => {
+		const variableName = `--z-index-${key.toLowerCase().replaceAll('_', '-')}`;
+		const value = APP_Z_INDEXES[key as keyof typeof APP_Z_INDEXES];
+		document.documentElement.style.setProperty(variableName, `${value}`);
+	});
+};
+
+export const useStyles = () => ({
+	APP_Z_INDEXES,
+	setAppZIndexes,
+});
diff --git a/packages/editor-ui/src/composables/useToast.ts b/packages/editor-ui/src/composables/useToast.ts
index 1ee8f4a2b4..7d07cdf249 100644
--- a/packages/editor-ui/src/composables/useToast.ts
+++ b/packages/editor-ui/src/composables/useToast.ts
@@ -9,6 +9,7 @@ import { useI18n } from './useI18n';
 import { useExternalHooks } from './useExternalHooks';
 import { VIEWS } from '@/constants';
 import type { ApplicationError } from 'n8n-workflow';
+import { useStyles } from './useStyles';
 
 export interface NotificationErrorWithNodeAndDescription extends ApplicationError {
 	node: {
@@ -17,15 +18,6 @@ export interface NotificationErrorWithNodeAndDescription extends ApplicationErro
 	description: string;
 }
 
-const messageDefaults: Partial<Omit<NotificationOptions, 'message'>> = {
-	dangerouslyUseHTMLString: false,
-	position: 'bottom-right',
-	zIndex: 1900, // above NDV and below the modals
-	offset: 64,
-	appendTo: '#app-grid',
-	customClass: 'content-toast',
-};
-
 const stickyNotificationQueue: NotificationHandle[] = [];
 
 export function useToast() {
@@ -34,6 +26,16 @@ export function useToast() {
 	const uiStore = useUIStore();
 	const externalHooks = useExternalHooks();
 	const i18n = useI18n();
+	const { APP_Z_INDEXES } = useStyles();
+
+	const messageDefaults: Partial<Omit<NotificationOptions, 'message'>> = {
+		dangerouslyUseHTMLString: false,
+		position: 'bottom-right',
+		zIndex: APP_Z_INDEXES.TOASTS, // above NDV and modal overlays
+		offset: 64,
+		appendTo: '#app-grid',
+		customClass: 'content-toast',
+	};
 
 	function showMessage(messageData: Partial<NotificationOptions>, track = true) {
 		const { message, title } = messageData;
diff --git a/packages/editor-ui/src/views/CanvasAddButton.vue b/packages/editor-ui/src/views/CanvasAddButton.vue
index ff7b37b4e3..108cf321e8 100644
--- a/packages/editor-ui/src/views/CanvasAddButton.vue
+++ b/packages/editor-ui/src/views/CanvasAddButton.vue
@@ -55,7 +55,7 @@ const containerCssVars = computed(() => ({
 	left: var(--trigger-placeholder-left-position);
 	// We have to increase z-index to make sure it's higher than selecting box in NodeView
 	// otherwise the clicks wouldn't register
-	z-index: 101;
+	z-index: var(--z-index-canvas-add-button);
 
 	&:hover .button svg path {
 		fill: var(--color-primary);