So lightburn is a frustrating app.  It is so close to being great, but out of the box it does not work well with GRBL and I can't see a good reason for it.  All the other GRBL senders just sense how the machine is setup and work with it, but not lightburn.  Anyway after lots of frustration I stumbled onto this document on there website for how to make your grbl machine work.  After spending some time playing with it I came up with the following adjustments and it seems to be working properly now.

First in the device settings fill in the following options:

• Our machine dimensions (about 350x450 mm), be sure to measure this accurately from the home position for your machine.
• Set the origin to the lower left corner (even though our origin is the upper right)
• Enable z axis support
• Enable the $J jog mode for smoother jogging.
• Turn off return to finish position, unless you have a safe position you want to send the cutter to.

On the console tab we need to add in two macros.  One will put the machine in laser mode and the other will return it to mill mode for regular mill work.  We will send $32=1 to enable laser mode, this has some laser safety like not turning the laser on unless the head is in motion.  And it removes a motion delay when you change the power.  $10=0 sets the machine into relative coordinates.  And G10 L2 P1 X-334 Y-334 offsets the origin relative to our home position so the origin is now in the lower left corner of the workspace.

Mill mode just reverses the above by turning off laser mode, using absolute coordinates, and removing the origin offset.

When you first start up lightburn, hit the home button, then hit the laser mode button to set the origin correctly.  Then at shutdown hit the mill button before exiting.

Finally for your job control set the origin of the job to the lower left corner and the start position to the current position.  That way you can jog to the corner of your work and start a job.  Keep in mind that by default this will start cutting at the current head position.  There may be a better way to handle this, I need to experiment some more.

If you want when jogging you can also enable continuous jog mode so that the laser moves as long as you hold down the jog buttons.  This works out ok, but the default move is very small so it can be fiddly to try and zero in on a point.

Anyway these changes seem to take us from broken to just a bit annoying.  Still I wish they had a more intuitive setup out of the box for GRBL.