Debian Font Manager (dfontmgr) is a GUI frontend for Defoma. You can see the fonts registered to Defoma, their hints, their status (which applications they have succeeded or failed to register), the applications using Defoma framework and information about the applications and the contents of their id-caches.
You can also register a font by drag-and-drop a font file, unregister a registered font, change the hints of and re-register a registered font. If a defoma-aware application uses an id-cache and if there's an identifier conflict (which means some fonts provides the same identifier) in the id-cache, you can indicate which font should provide the identifier.
GUI versions of some utilities in Defoma and psfontmgr are also installed.