I seem to remember older motorbikes having a position on the ignition key to have the parking lights on.
As soon as you’ve jumped the Twizy accessory battery from another car the system will power on and start charging from the Traction battery. It’s worth bearing in mind that once powered up you will want to leave the ignition on for 10 mins while the accessory battery gets charged back up. Turning it straight of after a power up the accessory battery will still be flat.
The problem is that the accessory battery is required to power up the CanBus and the rest of the vehicle’s systems to enable the 57-12v DC DC converter to switch on. CanBus was designed for conventional vehicles hence it uses 12v rather than the more logical approach of sourcing power from the traction battery.