Hey Paul,
you could ask @Greg (Route1WoodDesign). They sell this.
You could send @Greg the link to your rotary accessory and ask for “Switch, positioned on or at the QCW frame, that can switch between the original Onefinity Y-stepper and the Rotary accessory stepper, with cables.”
I would make the cable to the rotary long enough so that you can store the rotary somewhere without unplugging its stepper when not in use. You know, tin-plated contacts are not made for frequent plugging.