Find someone with VCDS or similar tool.
Go to 09 Central Electronics / Security Access: 31347 / Adaptations.
You can change these settings.
Stufe 1-3-5 is for driver's seat level 1-2-3.
Stufe 2-4-6 is for the passenger's seat level 1-2-3
IDE06089-ENG115738-Seat heater level current consumption allocation-Sitzheizung Stufe 1 obere Schaltschwelle,33.00 °C,30
IDE06089-ENG115737-Seat heater level current consumption allocation-Sitzheizung Stufe 1 untere Schaltschwelle,32.00 °C,30
IDE06089-ENG115740-Seat heater level current consumption allocation-Sitzheizung Stufe 2 obere Schaltschwelle,33.00 °C,30
IDE06089-ENG115739-Seat heater level current consumption allocation-Sitzheizung Stufe 2 untere Schaltschwelle,32.00 °C,30
IDE06089-ENG115742-Seat heater level current consumption allocation-Sitzheizung Stufe 3 obere Schaltschwelle,37.50 °C,30
IDE06089-ENG115741-Seat heater level current consumption allocation-Sitzheizung Stufe 3 untere Schaltschwelle,36.50 °C,30
IDE06089-ENG115744-Seat heater level current consumption allocation-Sitzheizung Stufe 4 obere Schaltschwelle,37.50 °C,30
IDE06089-ENG115743-Seat heater level current consumption allocation-Sitzheizung Stufe 4 untere Schaltschwelle,36.50 °C,30
IDE06089-ENG115746-Seat heater level current consumption allocation-Sitzheizung Stufe 5 obere Schaltschwelle,41.00 °C,30
IDE06089-ENG115745-Seat heater level current consumption allocation-Sitzheizung Stufe 5 untere Schaltschwelle,40.00 °C,30
IDE06089-ENG115748-Seat heater level current consumption allocation-Sitzheizung Stufe 6 obere Schaltschwelle,41.00 °C,30
IDE06089-ENG115747-Seat heater level current consumption allocation-Sitzheizung Stufe 6 untere Schaltschwelle,40.00 °C,30
These are my settings (also with alcantara seats) for driver/passanger level 1:
channel IDE06089-ENG115738-Seat heater level current consumption allocation-Sitzheizung Stufe 1 obere Schaltschwelle adapted from 33.00 °C to 21.00 °C
channel IDE06089-ENG115737-Seat heater level current consumption allocation-Sitzheizung Stufe 1 untere Schaltschwelle adapted from 32.00 °C to 20.00 °C
channel IDE06089-ENG115740-Seat heater level current consumption allocation-Sitzheizung Stufe 2 obere Schaltschwelle adapted from 33.00 °C to 21.00 °C
channel IDE06089-ENG115739-Seat heater level current consumption allocation-Sitzheizung Stufe 2 untere Schaltschwelle adapted from 32.00 °C to 20.00 °C
After some experimenting I finally set these values for 'always on'. I didn't bother changing level 2 & 3 because I never use them. The seat heats up quickly enough (for me) even with these settings. And I can leave it on for the whole winter. The seat gets just as 'hot' as you can warm it up with your body (with no heating).
You can also consider switching on the 'memory function" so you don't need to activate the seat heating manually on every start:
Module 08 / Adaptations
channel IDE01067-Retention of driver's seat heater level adapted from active for 10 minutes to active