If I sit in with another band, I usually create a new database and copy songs that are in other databases to the new one. But when I copy the song, the midi presets do not copy also. Any way to either copy all midi presets from one database to another at least? If the midi presets exist in the new database, would the preset selected in a song copy over? Or is there a way to do this easily?
You would have to separately copy your MIDI presets to the new database, then attach them to the copy of the song in the new database. There is no sharing of data between Set List Maker databases.
If you have a lot of overlap in songs between databases, you could check out BandHelper, which has a more flexible system of projects within an account, where songs and MIDI presets can be shared between multiple projects:
https://www.bandhelper.com/tutorials/projects.html