If you’re looking for a list of every code the snapmaker supports with nothing it doesn’t not even the official documentation meets that criteria, unfortunately.
This is the underlying firmware’s documentation, which is largely applicable: Gcode | Marlin Firmware
Here’s snapmaker’s incomplete attempt at modifying the Marlin documentation: https://snapmaker.github.io/Documentation/gcode/G000-G001
Here’s some more specific snapmaker codes: