"Free note" objects for alternate melodies

First, let me describe the issue:
In choir siging, sometimes a writer will suggests an alternate singing line. This is shown as small notes placed slightly before the beat to enhance readability.
-> You cannot use grace notes, because they have to refer to a note and are to far from the main note
-> You can add an extra voice, but the music bar is already quite full with 2 or 3 voices, adding another will not make things any clearer.

My suggestion is a 'free note' object, which is drawn relatve to a note or measure, like a text object, and does not influence the measue like a grace note does. It is literally a free note, and isn't played in playback.
If that isn't possile, is there a font where the characters are notes themselves?

I'm sure 'free notes' would also be useful in other cases, e.g. in a footnote explaining how to play tremolo's.