src/vs/workbench/browser/contextkeys.ts/WorkbenchContextKeysHandler/updateEditorGroupContextKeys
class WorkbenchContextKeysHandler:	private updateEditorGroupContextKeys(): void {
		const groupCount = this.editorGroupService.count;
		if (groupCount > 1) {
			this.multipleEditorGroupsContext.set(true);
		} else {
			this.multipleEditorGroupsContext.reset();
		}

		const activeGroup = this.editorGroupService.activeGroup;
		this.activeEditorGroupIndex.set(activeGroup.index + 1); // not zero-indexed
		this.activeEditorGroupLast.set(activeGroup.index === groupCount - 1);
		this.activeEditorGroupLocked.set(activeGroup.isLocked);
	}