Matthias Clasen:
How did you determine that NotShowIn=GNOME; doesn't have any
effect?
It should work fine to hide xpenguins from the places where
applications are normally listed in GNOME (the shell overview and
search).
It should? Then I'll try it again; I probably made some kind of
mistake when testing.
Thanks for your reply. It sounds like creating the blacklist is the
best available option after all.