Editing a chord in strum mode, is fairly easy with the arrow keys to move between strings and frets, and ‘k’ to mark a fret. You can remember your edited chord, with the ‘R’ key and associate it with a key (avail. version 0.8 apt release 1.0). Or you can push the chord on the stack with the ‘P’ key.
Updated chords with all your editing changes are printed upon quitting ‘-q’ vguitar.