does anyone know what to press to get both temperature gauges to move up and down together instead of having to do each one separately?

 

From the Porsche manual:

MONO mode
In mono mode, the temperatures on the driver's and passenger's side are synchronized and are regulated via button TEMP on the driver's side.

Switching on MONO mode

Press button AUTO and hold until MONO appears on the display.
Regulate the temperature on the driver's and passenger's side via button TEMP on the driver's side.

Take care!

 

You tried the procedure in the owners manual and it didn't work?