I'm trying to use MuseScore to drive an external synthesizer. For this to work, I really need the ability to send arbitrary MIDI commands. The "MIDI Action" tab in the text properties window looks like it would be exactly what I need... except that it doesn't seem to have been implemented! I found this blog that indicated it actually had been implemented last summer as a GSoC project: http://summer.cs.pdx.edu/blog/4186. But that code never seems to have been merged.
What are the prospects for getting this feature into MuseScore?