Just in case some of you haven't figured out how to get the filtered list feature working in MAMEWAH v1.61, you need to get the lastest catver.ini file
http://www.mameworld.net/catlist/. Once I downloaded the new file an used MAMEWAH Config 1.61.1 to generate my list using ROM Folder and -listxml (post .84 versions of MAME), the filtered list options showed in MAMEWAH.
Something else that I have notice is that there are two list for each platform in MAMEWAH, one is filterable and the other is not filterable. In order for your filter options to show, you need to select the list that is filterable.