There should be a thin blue wire inside the short cable on the motor which is used for the pedelec sensor.
If the pedelec connector was already fitted at the factory, I suspect the blue reverse wire is inside the heatshrink tubing.
Most single pole switches can be used as there is very little current being switched. On some of the earlier Magic Pies it was pre wired to the red switch on the throttle (before they decided to use it as a light switch.)
It doesn't really matter whether you use a latching switch or a momentary press switch, but make sure it cannot be accidentally knocked, or you might activate reverse when you don't want to.
All the switch has to do is
connect the blue and black wires together to select reverse. If your motor doesn't run in reverse with the blue and black wires switched together, you may need to enable reverse using the Bluetooth app.
Alan
