It's usually almost adorable how chunky the Quake 3 UI is, but if you try to use its "Skirmish" menu to play on a map against bots then it's just bad. That menu only displays 4 maps per screen and 64 total maps per gametype. Fortunately it was pretty straightforward to create a tiny UI mod that increases that to 12 maps per screen and 256 maps per gametype. (And honestly with RAM sizes these days, maps-per-gametype could have been much larger still... the old README file uses 128 MB of RAM as an example, which is cute.)
If you're using the CPMA mod then FYI that mod already has incorporated these changes, but otherwise a lightweight mod to improve this part of the UI may still be useful for you. I've recompiled the changes with the final Quake 3 game code to bring it up to date.