I was initially a tiny bit confused about the SHIFT button, but then I realized its meaning and operation is identical to the SHIFT button on a computer keyboard. In other words, press and HOLD shift, while next pressing the other relevant button. Easy peezey!
Numb or Nut, as said before Dwight is Alright, or maybe always right.
BTW, this sounds like a new incurable Royal Accordionist's inbreeding disease called Anaestesia's Nutty Numbness, to be further discussed on a synthesizer forum ...
PS Imagine a shift button on an Acadian Model #4 and what could happen if you press it at the same time closing a stop ... a hatch opens and a beer pops up? An idea for you Bryan maybe & the newest # 13.5 XL mark II model. - Nout