"Piano Roll"
Could what I call a piano roll (for want of a more correct name) be added, possibly in the tremolo part of the palette. It consists of 1,2, or 3 angular lines or bars similar to the tremolo bars but longer, maybe the tremolo bars could be modified to be stretchable and also the angle should be adjustable to set them parallel to the notes beam, this is probably a jazz symbol and for reference I will mention Oscar Petersen's "Hymn to Freedom" however I've seen it in many other compositions.
Comments
Could you a picture of what you are talking about? I haven't seen a published transcription of the piece you mention to know what you are talking about.
I'm guessing maybe you mean the way tremolo is occasionally notated (both in jazz and classical, and not just for piano) with two beamed notes and the tremolo sign within the beam, as in this example:
http://en.m.wikipedia.org/wiki/Tremolo#/image/File:Fingered-tremolo.png
If so, then I agree this makes sense to support someday.. Meanwhile, though, it doesn't mean anything different from the standard tremolo notation as far as I know, so you can just use that and achieve the exact same effect..