To make music-sheets for beginners or to make the software more complete, it would be nice to have strum editor, a dialog like the chord editor, but to setup upstrokes and downstrokes patterns that with a chord you can fill a beat with a little work. As in the chord editor you could have various predefined patterns to make editing even more fast.
Having an easier notation for strumming. It would be interesting that you could use "rhythm slashes" and appears in an "printed-like" fashion on the top of the staff.
And it would be good that you can choose where does the chord charts appear, above the note, above the first note of the strumming pattern or on the top of the sheet and only the name above the note.