See here and here. It’s not recommended to change these settings at runtime as noted, and any changes you make won’t be persistent through a restart.
SET_TMC_CURRENT¶
SET_TMC_CURRENT STEPPER=<name> CURRENT=<amps> HOLDCURRENT=<amps>: This will adjust the run and hold currents of the TMC driver. (HOLDCURRENT is not applicable to tmc2660 drivers.)SET_TMC_FIELD¶
SET_TMC_FIELD STEPPER=<name> FIELD=<field> VALUE=<value>: This will alter the value of the specified register field of the TMC driver. This command is intended for low-level diagnostics and debugging only because changing the fields during run-time can lead to undesired and potentially dangerous behavior of your printer. Permanent changes should be made using the printer configuration file instead. No sanity checks are performed for the given values.