When I looked, I looked in the wrong place. The G code generated by Snapmakerjs for CNC work had only M3/M5 (spindle on/off) and movement records. No special commands whatsoever.
Where I next looked was the resistance value between pins 5 and 7 of the carver and laser modules. Results - print module 82K (nominal), carver 10K, laser 200 130R, laser 1600 130R.
Methinks this is how the Snapmaker firmware determines which module is attached.
If one wades through 8.8 - DIY Laser Module, one will see R4 in a PCB layout. My guess is this is 130R.
And @clewis, your “I know there is a pencil holder tool that has no electronics in it” maybe at challenge - a 10K resistor perhaps hiding in a corner.
At a later time I will test my theory by fitting a 10K resistor and issue M3/M5 to signal a dispense.