Well, it does not offer a lot of useful options for mGalaxy, in fact i was mainly using it to parse "clrmamepro" databases files created from datomatic (
http://datomatic.no-intro.org/?page=download&fun=dat) which does provide some filtering capability and export them as xml for mGalaxy (clrmamepro also offer a way to validate your rom set, missing ones and much more in fact). This also allow you to filter unwanted roms without actually deleting/moving them or doing it manually.
So to resume my process was :
- export clean/filtered clrmamepro dat format from datomatic
- import in clrmamepro and scan from missing rom etc
- export to xml format for mGalaxy (with a few changes needed...)
I think you should add a function to be able to import an clrmamepro dat/xml as a start instead of a directory, this would allow people to use any clrmamepro databases which i think are common (and/or easily share rom databases than can be checked with clrmamepro). The (clrmamepro exported) .xml format should be really easy/fast for you to add, while it may require more time to add the (clrmamepro) .dat format and may be useless.
You'll find an clrmamepro xml file format below in case...
Edit: i added a screenshot of clrmamepro in use just "for fun", here we can see that i'm only missing 4 snes and 10 genesis roms from the (filtered: us,eu,fr) no-intro sets, while i does have a lot more roms in the folders (japan, bresil, etc..)