If you manually edit the .adl file, you can drag/drop files.
I've been creating MIDI backings (drums, bass, guide guitar - whatever) and using Roland Virtual Sound Canvas to convert them to a mono wav file.
After that just take a 'boilerplate' .adl from a single track 'song', change the name, set the tempo to match that of the original midi file, set the track one wav name to match your backing track, and set the track duration to match the length of the wav file.
At this point the click on the MR-8 will be in sync with the backing wav, and an unlimited number of tracks can be moved between the Mr-8 and something like n-Track without having to line up tracks.
Sounds complicated, but by naming your wav files after copying from the MR-8, it's easy to just drag/drop various combinations of tracks back to the MR-8 to record against. (I have almost 20 tracks of various 'takes' that I'm mixing in n-Track to create a tune with just two guitars and a single vocal.)
(...and I've noticed the 0D File error comes from the MR-8 playing/recording past the max time in the .ADL, but it causes no harm - the extra material is still recorded...)