Sync to Rekordbox
Build it on your phone. It's in Rekordbox.
A playlist you put together in Rimeo lands in your real Rekordbox library with the same name, in the right folder, in the same order. There is nothing to export and nothing to import.
Backed up before anything is written
Rimeo copies your library first. If any part of the write does not come back clean, it puts everything back the way it was.
Run it twice, nothing doubles
Rimeo sends the difference, not a copy, so running Sync again changes nothing. The playlist ends up exactly as you left it in Rimeo, so keep editing it on the phone rather than in Rekordbox.
You can watch it happen
Four stages, reported as each one finishes. You see your library was backed up before a single track moves.