Hey, currently, no, it's not possible to assign the encoder's button to act like the performance switch.  The encoder's button changes whether the right footswitch increments or decrements presets, and we didn't think it was a good idea to give it a more central function than that given than it can be hard to hit depending on what kind of shoes you're wearing. You are the second person to ask for that particular option though, and we will at least discuss it internally.