Is the Vref trimmer relevant on TMC2208 in UART mode? I'm going to use TMC2208 stepstick in a printer and the firmware can control via UART the current during printing and during holding (static, no movement): the firmware has an explicit setting for running current and for holding current.
In this case, should I care about the physical trimmer which controls the Vref?
I tried to understand the TMC2208 datasheet (page 50) when it's talking about current control but I don't understand whether the Vref becomes superfluous or it still acts as a maximum value which the UART must obey.
The potmeter does not work in UART operation, see e.g. this quote:

You don't have to fiddle with jumpers to set your micro-steps, just
change it in the firmware, and you can dynamically change the amount
of current going to each stepper motor (no more adjusting that small
potentiometer on the driver board) just by sending a GCode command
(M906).