Renoise doesn’t import midi files, does it?
yes, it does, though the implementation of this feature is not 100% complete at this beta stage: what can occur more frequently is that some kind .mid of files are not loaded correctly.
.mid files are loaded as a standard .rns file
cool. I’m gonna play around with BFD’s midi files. 
Renoise cannot export as Midi.
you should use a virtual MIDI cable as MIDI out and use a MIDI sequencer to export the RNS to MIDI. I’ve never tried it, but I should do it some day…
Once I’ve asked a similar question and received these answers