Hi and thanks for your question. This is really a "transpose" function. Right now, this isn't available in MIDI Designer. We're hoping to get that feature out soon.
Thanks so much for the kind words and also the notes about the YouTube tutorials. We do know that we're hearing from users less and less, but we do not know HOW you are getting your info. Great to know.
If you love the app, please leave a nice review for Pro, Lite, 12, or XW (or all of them, really)... reviews drive interest in MIDI Designer and keep the project rocketing forward.