old thread, but if someone is searching for info, here's a bit more.
I just successfully changed the names that are displayed for Sega Model 2 roms in the game lists.
(don't change the actual rom names!!)
The pitfall was probably the extension .mln (n=emulator number, you must replace "n" with the number that mala assigned to the emulator)
Here's a rundown of what I did in the gamelist editor (it worked fine).
1. Click the emulator tab & select the emulator that you want to make a gamelist for
2. Click File>Open &
take note of the extension of the "All Games" list.
It will be different for each emulator & varies depending on how many emulators you have.
Sega Model 2 is .ml21 on mine. (way too many emulators, most never played)
3. Edit the list to your liking. On the "Destination" side, double click the rom that you wish to change the name for.
Type in the NAME box the title you would like to show up in the list.
Don't mess with the rom or path boxes.
4. Click File>Save. Make sure that under "save as file type" it says (whatever you named the emulator) gamelist files (*ml##).
Where ## is the number of the emulator that you took note of in step 2. I typed the extension along with the file name just to be sure.
Here is an example: