So as not to lose the context:
As I mentioned earlier, an Arduino Uno will be grossly underqualified for the speeds required for a large CO₂ machine.
The CNC Shield is intended for plug-in PCB stepper modules, not the TB6600 drivers. It lacks the screw terminals generally used for reliable connection in large machines and those pin-header connectors will cause severe intermittent problems on large machines.
Running NEMA 23 size stepper motors from a 12 V supply will severely limit their maximum speed, because the drivers won’t have enough headroom for effective current feedback. Typical large lasers run from 24 or 36 VDC supplies.
That is the bare config.h file to configure parts of the GRBL source code; there are many other header files in addition to the source code files in the GRBL repository. As I stated earlier, you must adapt the default configuration values to match whatever your machine turns out to be.
You have a long way to go before LightBurn becomes relevant to your project and, because this is a forum for LightBurn software, you will get better and more specific assistance from a site devoted to builders starting with a class assignment and a parts list.