In our workflow, people will import model sets from one KSP/BIP to another and before we know it we have HUNDREDS of cameras in our lists.
Currenlty the only way to clear them that I could find was to click, press delete, click, delete, click, delete. and then you get a dialog warning you that a camera is in use in a Studio - GOOD this is awesome that it does this, so KS is keeping track - so there HAS to be a way to either select all un-used, or delete all un-used enmasse, no?
(we also have this issue with Image Styles and Environments, but Cameras is the biggest hassle)