As the subject says... and like the bug solved in 4.5.2, it seems. Comics show in /share/apps/comic, but don't appear in menu. I'm more than a little lost - new os, new desktop (Sabayon, if that is of any importance). So, what do I do now? That widget looks like a much welcome drain on my productivity and I'd like to start procrastinating right away.

Please try running "kbuildsycoca4" - simply entering this in KRunner and pressing enter should be enough.
Then logout and back in again to ensure the Comic applet is not performing any caching of the list of installed comics.