So, I've found, what I think is the latest public catver.ini file here (for MAME version 0.221 so far. Haven't found any for 0.222):
http://www.progettosnaps.net/catver/And now I want to do some filtering in Attract Mode so I looked around and found some good example filters.
So I can filter up the roms in Maze games, Driving games etc.. . . Great!

My problem: How do I know what other categories I can filter on?
For example; is there a Category for "Games including horses"? How do I find out? I can open up the file in an editor and search for horses and hope for good luck. But maybe the category is called Equestrian instead? I'm not sure what to search for.
So, how do I know what different categories there is in the catver.ini file?
I've searched and searched, and maybe just my google-mojo is bad

, but I can't find a list of what categories there are in catver.ini.
The closest to a solution I've found is to instead look in the catlist.ini file included in the above linked file.
In that file the categories have their own rows, and perhaps I can do some scripting to sort out just the lines starting with "[" to get something resembling a list of categories.
But then I have to learn to do scripting to edit text-files.

Can anybody help me where to find this information?