extensions/references-view/src/types/model.ts/TypesModel/_move
class TypesModel:	private _move(item: TypeItem, fwd: boolean): TypeItem | void {
		if (item.children?.length) {
			return fwd ? item.children[0] : tail(item.children);
		}
		const array = this.roots.includes(item) ? this.roots : item.parent?.children;
		if (array?.length) {
			const idx = array.indexOf(item);
			const delta = fwd ? 1 : -1;
			return array[idx + delta + array.length % array.length];
		}
	}