first, make sure you have a mame-1.ini file in your MameWah directory... or any mame-x.ini file where x is any number other than 0. Once you have that...
Start up mamewah. Hit 2. Choose select custom list and pick the list that ISN'T the main list.. I think it says FILTERED as default... it might be blank totally if you made a new file, at least it was for me... just scroll to that other list and choose it.
Now you're in a filterable list. Hit 2. Choose Games List Options. Choose Generate filtered list. Now it's just like it always was in MameWah. Select a category (BIOS, Years, Manufacturers, etc) and change them as you see fit. These option only show up of course if you have catver.ini installed and set up in MameWah.
For your list, you'd want to pick clones - Only if better than parent, and I believe there is a setting for preliminary games, which are games that don't quite work yet... shut those off.
hope that helps.