The idea would be a series on note heads only representing rhythmic placement along with pitch, no stems or beams. So for instance, I would have the normal note head on the beat, but then I would show beat divisions with say a plus note head, or an X note head. The only issue being that I would like the note spacing to look about the same as if it was notated with proper rhythms. (If that makes sense at all) The first thought I had would be to write 8th notes, but then hide the beam/flag and stem. That way I would still see the “correct” note spacing. Hiding the stem is a no brainer, but hiding the flag or beam is a little less easy.