As the title suggests, it would be really nice if you could set one or more file formats for each platform so as to make the whole "scan for added roms" feature work nicely.
Let's use the Sony Playstation as an example, good dumps are usually in a bin+cue format, by setting the aforementioned platform file format filter to only pick up .cue files, your psx games folder would be correctly scanned with the "scan for added roms" feature without creating a mess of duplicates etc.
Overall it shouldn't be really hard to implement and it's something that will definitely benefit launchbox in the long run, no one likes to keep adding games "manually".