Hi Frosty - I use my own standalone MAME installation, pick non-merged (which is the format my 300 rom curated set is in), select all filters on the exclusion page to filter out all the crap, keep the trackball, lightgun and spinner games because my cab has all that, and prioritize North America & 2 Players. After scanning it imports 14,398 roms.
Just one more thing, I’m confused what changed here. Months ago I was able to import my 300 rom set no problem, but now the MAME plugin doesn’t support it and it needs to be added in? Why was it removed?