src/vs/workbench/contrib/notebook/browser/view/renderers/cellDnd.ts/CellDragAndDropController/onCellDragLeave
class CellDragAndDropController:	private onCellDragLeave(event: CellDragEvent): void {
		if (!event.browserEvent.relatedTarget || !DOM.isAncestor(event.browserEvent.relatedTarget as HTMLElement, this.notebookEditor.getDomNode())) {
			this.setInsertIndicatorVisibility(false);
		}
	}