ReaperOSC files are the only way to get Reaper to issue an OSC command.
What I've had to do is pick any of the actions you can bind that you think you'll never actually need to use, which has the appropriate parameters for the message you want to send, then cause that action to happen some how.
You'll notice that Default.ReaperOSC mentions nothing about opening the MIDI Editor, so there's no direct way there. What you'll likely need to do is write a short script to do two things:
- open the MIDI editor
- something else that
is in Default.ReaperOSC
Then, make the method you currently use to open the MIDI editor run that script instead.
For example, I use track select to send out an OSC string (because I don't need to bind track select to its usual purpose) - but I needed to pass an "on/off" value - it'll be different in your exact case
Code:
...
reaper.SetTrackSelected(reaper.GetTrack(0, srTk - 1), srVal)
...
Code:
TRACK_SELECT b/track/@/onOff