src/vs/workbench/contrib/debug/browser/watchExpressionsView.ts/WatchExpressionsDragAndDrop/drop
class WatchExpressionsDragAndDrop:	drop(data: IDragAndDropData, targetElement: IExpression): void {
		if (!(data instanceof ElementsDragAndDropData)) {
			return;
		}

		const draggedElement = (data as ElementsDragAndDropData<IExpression>).elements[0];
		const watches = this.debugService.getModel().getWatchExpressions();
		const position = targetElement instanceof Expression ? watches.indexOf(targetElement) : watches.length - 1;
		this.debugService.moveWatchExpression(draggedElement.getId(), position);
	}