Posted by JustinT on 22, 2000 at 4:03 PM:
In Reply to: How to make a list of just vertical games? posted by Mike on 22, 2000 at 3:25 PM:
The Mac version (MacMAME) supports custom lists (maintained by a Mame fan). Here is the link:
http://www.tznet.com/cmader/macstick/sortfiles.html
Not sure if horiz/vert grouping is there, but it's a good place to start!