You need two macros - one for “Use Laser” and one for “Use CNC”. Their contents will be:
Use Laser:
$10=0
$30=1000
$32=1
G10 L2 P1 X-750 Y-750
Use CNC:
$10=115
$30=1
$32=0
G10 L2 P1 X0 Y0
Prior to using the laser, click the ‘Use Laser’ macro button, and when you’re done and want to switch back to using the CNC, click the ‘Use CNC’ macro button. To define a macro, go to the console and right-click one of the buttons. Copy the code I wrote above and name the button accordingly.
The ‘Use Laser’ macro sets the machine to report positions relative to the user workspace, sets the spindle max RPM parameter to 1000 (the GRBL default), enables laser mode, and zeros the machine origin to the front-left. The ‘Use CNC’ macro sets everything back to where it was before that.