src/vs/base/browser/ui/splitview/splitview.ts/SplitView/orthogonalEndSash
class SplitView:	set orthogonalEndSash(sash: Sash | undefined) {
		for (const sashItem of this.sashItems) {
			sashItem.sash.orthogonalEndSash = sash;
		}

		this._orthogonalEndSash = sash;
	}