The Keytrigg is still a mystery for me.
Can someone shed some light on this?
When you play a note on a keyboard there's a "gate" which is opened for this note. This gate is closed when the key is released (ie when the NOTE OFF MIDI message is received). If the PROGRAM is polyphonic you get a gate for each key pressed. Those gates are ORed to form a gate at PROGRAM level which is opened as soon there is a key pressed and closed when no more key is pressed. "KeyTrigg" is the PROGRAM (MONO) module that provides this composite gate.
The KeyTrigg gate is used to trigger PROGRAM modules that need a TRIG to start processing the Sequencer, Galaxy, Env2D and LFOs 1 and 2.
That said, you're right, the availability of this gate at VOICE level makes no sense. We should remove this output form the connection popup menu.