Official comment
As posted here, the following functions are user-mappable:
Well now, we're not going to let good gear just sit on the shelf, are we?
The XP1 is definitely mappable, here - check this out...
Buttons that can be MIDI Mapped (items with / + shift means both):
- 4 Beat Loop + SHIFT
- Quantize / + SHIFT
- Load / + SHIFT
- Loop In / + SHIFT
- Loop Out / + SHIFT
- Slip Reverse / + SHIFT
- MT / + SHIFT
- Beat Sync / + SHIFT
- Page < + SHIFT
- Page > + SHIFT
- Silent Cue + SHIFT
- Semitone - / + SHIFT
- Semitone + / + SHIFT
- Encoder turn / + SHIFT
- Encoder push / + SHIFT
- Hold
As noted in bold, the encoder IS mappable.