Peter, greetings. I’ve been using LB for design and gcode to run my CNC plasma system for about 8 months now, making refinements to the process along the way. I have the process very stable, reliable, and repeatable right now and consider it complete until LB may choose to implement direct support of plasma process. I’m happy with it for sure. I’ve used LB on CNC laser system I’ve had going on 3 years and like it so much I was determined to adopt LB to plasma process. So for plasma use, I post process the LB generated/saved gcode using a VIM editor script; the script replaces M3 and M5 commands with code blocks to perform torch touch off which sets the Pierce Height and then transitions to Initital Torch Height before each cut and to retract the torch after each cut. I use a stand alone THC also, Proma THC SD.
The latest version of my VIM script is in this thread/post - Update on plasma use case success, albeit post processing gcode - #12 by bLouChip
I should add that a key element of my post processing method is to use the LB device type GRBL-M3; other LB grbl device types make use of grbl laser specific behaviors such as use of M4 variable spindle power relying on G0 move at effective S0 rather than M3/M5 combinations.
I’m happy to share what I have discovered and offer assistance if needed.
Cheers,
Lou