Is there a way to reset the TMC5072's registers from software?
There is no software command for resetting all registers of the TMC5072. You'll notice that when using the TMC5072-EVAL and TMCL-IDE GUI, there is a button that resets the device. However, this is implemented by writing the default settings to each register. It is not performed by a single reset command.
The TMC5072 can be reset by a power cycle of VSA, 5VOUT, or VCC_IO. The VCC pin is not monitored and will not reset the device if cycled. Please see section 20 of the TMC5072 datasheet for more information on how to reset this device.