Which GPIO pin is connected to the physical knob on the side of the lilygo T-Watch S3?

koshincml

On the LilyGo T-Watch S3 2020, which GPIO pin is connected to the physical knob on the side of the watch?

I'm aware of the schematic here but I can't find the knob in that schematic.

I have also looked through the pin definitions in C code here but I see no mention of the physical knob.

The knob I'm referring to is this one:

teastain2

Do you have a Watch 2020-V3 or an Watch-S3?
Makes some difference.

On some models the swich is GPIO 0.
Useful as a user input and for entering download mode.