I'm looking forward to buy GLI early next year and started to compile a list of mods. The list obviously has adding ESP/Traction Control button, and AWE Tuning how-to is very handy.
Unfortunately, they did not provide the schematic, so I made one for myself.
I've noticed that for simplicity they permanently connected pins 3 and 4 of the ESP button to 12V power outlet. In this case the button is going to be backlit all the time (at least all times when power outlet is hot).
I have an idea to connect the backlit pin 3 to vehicle backlit circuitry by tapping on the similar pin of the other button, for example to the Tire Pressure Monitor button located in the glove box.
On the left side is the schematic of 2011 Golf ESP button. On the right side is the schematic of 2012 Jetta TPM button with proposed ESP button wiring.

Pin 3 of the ESP switch is connected to vehicle back-lighting circuitry, pin 4 receives 12V from same pin of TPM (this wire is already protected by 5A fuse).
Pin 6 goes to the vehicle ground. Pin 5 goes to pin 39 of the ABS module as described in the original DIY.
Note that I did NOT implement this idea yet, but I'm going to do this as soon as I get my new car.
P.S. ABS module connector pin 44 marked as "ESP_LED (optional)". Some cars have ESP switch with indicator light that uses this pin to indicate that ESP is off. However, it may still work on our cars too.
And pin 3 of the ABS module is marked as "Auto Hold input". Sounds like another possible mod: Auto Hold On/Off switch
