slash noteheads and playback
There should be a way to say 'never play slash noteheads'. In a jazz chart you want the noteheads to indicate where the chords should be sounded. The 'fill with slashes' gadget is ok but you can't create a rhythmic feature that is not quarter notes. I guess 'never play' isn't right, never play them as staff notes, they should behave as slashes, triggering the sounding of the indicated chord.