@WS custom <command>to make sure they do not conflict with others.
G28, the plugin will match
G28 X Y, or
G28 Zas well. Or if you enter
G29it will match
G29 Tas well.
G28 Zhere. The whole line needs to be exactly the same for this effect to trigger.
G[0-9]+would match any G command sent to the printer. You could use
M50[0-3]to match any of the EEPROM management commands, M500, M501, M502 or M503.