There's a documentation by Red ("Mapper keys 1.6 by Red!"). Which says:
QUOTE START
F9: /Rebuild item protos (Librarian menu - need librarian=1 in cfg)
F10: Quit/Rebuild proto lists (Librarian menu - need librarian=1 in cfg)
F11: /Rebuild all (Librarian menu - need librarian=1 in cfg)
- [ Librarian mode ] -
The librarian menu can be toggled on with override_librarian=1 in the cfg, note
that while it's enabled you can't save your map.
- [ Editing PRO files ] -
To get the PRO files to be editable, on the same drive that you run the mapper,
create /fallout2/dev/proto, and in it place the directories critters, items,
scenery, tiles, walls and misc. Once that's done you can edit the PRO files by
simply Right-Clicking on them with the mouse and Clicking the Edit button (or
pressing E). You also need to make sure that librarian is set to 1 in the cfg
(and preferably librarian_override still set to 0 if you still want to be able
to save maps).
An important note is that each PRO contains it's own PID in the file. If you
copy a PRO file to overwrite another one or create a new one at the end of the
list, you'll need to make sure the internally contained PID matches the it's own
critter.lst line number. You could hex edit it, or:
- edit the proto, thus creating the text file reference;
- rebuild the protos (F9, see above, though you might need to use F11).
Here's a sample of how it looks on my drive for reference (in hopes it looks
good in whatever media you read this in...)
E:\
\---fallout2
\---dev
\---proto
+---critters
+---items
+---scenery
+---tiles
+---walls
\---misc
END QUOTE SCRIPT COMMAND DEV OVERRIDE POWER
So, I'd say Librarian is a function when you want the mapper to edit proto files.
And override_librarian enables a menu (?), but you can't save the map... but I never tested it.
Btw, regarding the internal PID, I have not yet (!) found an issue in-game (...), but it messes up the mapper's "P" hotkey. Which is a very useful hotkey.