I'd like this, too.  I currently use a Tag for Snappers, but a filter would work even better.

The reason I tag snappers is I started (and have gotten way behind) to replace all my snap cases with keep cases.  I scan the entire snapper cover and then print the cover to use in a keep case.  I keep the cardboard snapper covers and a couple of the plastic cover parts (in case I ever want to give away or sell a DVD).  Often my DVDs wind up in a pile instead of neatly shelved -- and the keep cases protect the contents much better than the snappers do.  I've got a lot of warped snappers -- the cover, not the disc.  At least in a keeper I have less to worry about.

Lately I've been converting from snappers to slimpak covers.  They take up less room, but don't stand up on their own as readily as the larger keepcases.