Apparently it is possible to invoke the encoder routine without PC by the following sequence:
Before you turn on the key, apply full throttle and the right brake lever. Turn on key and hold throttle and brake until wrench icon appears. The encoder routine will start automatically. First the wheel will lock to a position then it will slowly turn until it is calibrated.
I didn't yet have a chance to test. Also I wouldn't recommend to try without having first lifted the rear wheel off the pavement. The motor would not achieve zero phase angle under load and this could result in a mismatch. Also don't run this routine unless required, eg after an encoder exchange or adjustment.
Nevertheless this is, if it works, a very elegant feature that should come quite handy in certain situations and for those without CANBus adapter.