Is there a way to manage the effects browser?

I have a bunch of obsolete (or useless-to-me) effects/transitions/themes etc. that clutter that lower right browser. I would like to get rid of - or at least hide - many of those items. Is there a way to delete or manage them? (PS: I know I can use Motion to create folders for favorite effects, themes, etc. but I would still like to houseclean a bit so I don't have to scroll through all the items I never use.)