increment / decrement all marked values

[XORadmin]

Yes, it's exactly what I was thinking too. I suspect that to make it useful it would have to be more or a 'select' type option rather than in the Nerd Menu, which I imagine would transpose all notes (in that pattern). Practically, you might want to transpose the first 10 notes up a 5th, but not the next 5 notes, etc.

You can mark and transpose the marked parts indeed through the nerd-menu.
SHIFT+DOWN in marked mode is already used to mark all
SHIFT + CURSOR LEFT/RIGHT/UP/DOWN is already used in the new version for another mark possibility

Leaves only the nerd menu for functionality. For now as you know, transposing a semitone and a octave are possible. These could be changed into a increase/decrease which would have the same effect for transposing but would include also other functions. Not sure if you only asked for transposing.