Here's what I do:
1. hook up car to Motorhome, make sure it's in AWD mode
2. Engage 2021 Buick GX Essence parking brake
3. Press & hold down Engine Start / Stop button (WITHOUT brake pedal) until lights up, approx. 3 seconds; manual says once, but nothing happens unless button held for approx 3 seconds
4. Shift gear to Neutral, WITH brake pedal applied. (Car does not start). Leave in Neutral.
5. Release parking brake
6. Disconnect negative battery cable, cover terminal with a plastic battery cap, ensure no contact possible during tow mode.
7. Keep tow speed under 70 mph (113 km/hr).
No problems, driven over 7000 kms towing, 2 years.