So I deleted the silverbullet.db* files, shutdown and restarted deno, and when SB started up again it re-indexed everything. And now I have only one Library listed.
Looks like I lost a couple of “library-related” things, but it’ll be easy to re-do.
I think what happened was, I wanted the default Library to be LIBRARY (to match PLUGS, SETTINGS, and STYLES). So I created a LIBRARY folder but then I couldn’t figure out how to get rid of Library. So I left it for another day and never got around to fixing it.