I use Mp3tag not only for mp3, but also to tag movies in mp4 format. Mp3tag is by far the fastest and most stable program for tagging mp4 out of all programs that I've tried - awesome work!
In addition to writing those mp4 tags, I would really like to use Mp3tag to create NFO files for Kodi and other media managers, since a lot of them don't support internal mp4 tags. So I tried to write an export configuration script and do the following with the export function:
Unfortunately that's not perfectly possible in Mp3tag, because it would require the export function to write a separate output file for every source file. Right now, it's only possible to do this on a per folder basis.
It would be really great if you could add the possibility of creating one output file per source file with the export function. I think that could be a nice little feature for other use cases as well.