Can saved searches be moved into collections?
One can move a collection into another collection as a subcollection by simple drag and drop. While saved searches behave like collections in other respects, it seems that they can not be dragged and dropped into other collections. Is that by design or a bug?
Regarding dragging one search into another one: I had not thought about that until you mentioned it, but it would make sense for that to mean creating a new search that combines the parent search with the child search via an AND operation. If there is a discussion of this drag and drop for saved searches somewhere, I could make this suggestion there.
Another method is to make saved search collectable under collections, so you'll be able to find them easily in the normal navigation tree, while currently they're all at the bottom and impossible to do any kind of organization.
Modify the collection tree to attach saved searches directly sounds a bad idea to me, this will make significant changes to the collection structure for a edge use case.