GCode based systems use the "Set Origin" button in LightBurn to do the same thing. You jog your laser to the position you want your job to start from, hit the "Set Origin" button, and then you're free ...
If you do not set this value, LightBurn will use the same speed as the G1 moves. GRBL and Smoothieware use the S-Value (spindle speed setting) to control the PWM power output to the laser. This ...