Posted by Eric:
But modifying a search doesn't seem to work.
When you modify a search, it simply creates a "new search", so you need to give it a name to save the search to use again.
If you use the same name for this new search, it creates an additional saved search (you will have 2 searches with the same name). You will need to "forget" the saved search which is incorrect so that old saved search is deleted and therefore you end up with only one saved search with that name.