I'm assuming you want to do the momentary octave up effect? Where you step on the switch to make it go up and let go and it comes back down?
Start by defining a per-preset switch that's momentary and assigned to Control Switch 1:
Next, assign that per-preset switch to a switch on a layout on your FC-12. I used switch 2 on layout 1 on my FC-6 here:
Now add a Pitch block to your preset and set it to "Classic Whammy" mode, Up 1 Octave like so:
Right click on the "Control" parameter and set the modifier to be Control Switch 1. You can play with the Attack and Release parameters to control how fast the effect climbs from 0 to +1 octave when you press the switch and how quickly it descends from +1 octave to 0 when you let go of the switch. I have it set to the default 10.1 ms here and it feels pretty "zoo station"-esque:
Right click on the Bypass parameter in the Pitch block and assign Control Switch 1 as the modifier. Make sure the bypassed and engaged values are correct. And turn the attack parameter to 0 ms and release parameter to about 11 ms.
When you step on the switch on your FC the effect will engage and go from unison to +1 octace in 10 msecs. When you release the switch on the FC the pitch will descend in 10 ms and after 11 ms the block will be bypassed.
Edit: upon further contemplation it might easier to use auto-engage with fast position detection. Then you don’t have to fiddle with the release time on the bypass modifier setting every time you change the release time on the control modifier setting.
