I started working on this item but I'll have to postpone it and do some preliminary work. The data collected in the Usage database does allow to reliably find unused favorites. As explained in
another thread, the challenge here is that unused favorites, because they are unused, are not in the database. So it is not possible to get a list a unused favorites directly from the database.
I thought that I could scan favorites in the QAP menu and flag those not found in the data. Unfortunately, because the data collected is location-based (merging data from two sources: Windows Recent items folder and QAP menu usage), and not QAP menu/favorites-based, the database does not allow to identify reliably favorites that are in the menu or not. Doing this would require a unique identifier for favorites (that does not exist) or additional info like the favorites's parent menu.
So, for now, I'll rename this item from "Special search for unused favorites" to "Identify favorites reliably in the Usage database". When this will be done, it should be possible to identify absent favorites reliably.