It's inside "startup.arc". You have to extract the files from there and they can be edited (And no, it can't be opened with WinRAR or 7zip. You need a copy of arcutil.exe).
That's because Butterfly is configured to support DDR A and partial DDR A20 2019-09-03 so the tables in the database aren't updated for the new songs. Play older songs and the score will be saved, but the new ones, impossible for now.