Soo it took way longer than anticipated (because I needed to make the new UI more stable before adding MIDI support, also various other topics got in the way), but the latest alpha (v2.809) includes first basic support that will now be completed during the next 1-2 weeks.
Currently the UI and functionality is still very limited and only targetet at early testers / advanced users:
Basically you open the "MIDI Event Viewer" to figure out which are the correct command and control values you want to target, then you configure your trigger to match that. For example in the screenshot above I have configured a trigger that executes when the Note On Command (159) is received AND the note/control with number 40 is also on/active.
If you assign the predefined action "Run Apple Script (async in background)", the Apple Script can receive the current value/velocity/whatever by using a script like this:
#example to change system volume, max midi value is 127:
set volume output volume (midiValue / 127) * 100
I'm not at all a MIDI expert and only own one device, so any suggestions would be great. The UI to configure the triggers will be improved and things like "repeat" will be activated over the next 1-2 weeks. MIDI Output will be added after that.