… ah, o.k., you want a harmony note for every melody note that is played (whereas the chord track itself will just give sustained chords)?
I’ve just tried duplicating a MIDI melody Part three times, transposing each, such that at least the first block of notes formed a chord to fit the first chord in the chord track, then used the Chord track option “Map to Chord Track”, on the three selected Parts, but the result is disappointing… it merely transposes notes that are outside the current chord to fit, but doesn’t necessarily make a useful chord.
…even just using “Follow Chord Track” in the Inspector of each MIDI track, using “Single voice” (and then selecting “Alto” etc.) is not really convincing 