Multiple fixture setup

Have a look at G10 L2 .. and G10 L20 ...
linuxcnc.org/docs/html/gcode/g-code.html#gcode:g10-l2

As far as i can understand, you are looking for this
linuxcnc.org/docs/html/gcode/coordinates...#_coordinate_systems
Below should be confirmed as i can not do tests right now:
One way to set these should be by using the "touch off" button in the Axis GUI and choosing the correct "fixture" from the drop down menu and setting the correct value for the selected axis/joint.
On older versions of LinuxCNC the drop down menu had G54, G55, etc listed, new versions have P1, P2 etc that should corelate to G54, G55 etc. I think it means Part 1, Part 2, etc, but this is just my guess.
Setting the machine with MDI to G55 etc then jogging to the part position and touching off should also work.

not sure if when you enter an offset value for x,y,z the offset is from where you set the origin or is it from machine zero?

G10 L2 ... refers to machine zero (ie if you already know the offset values from machine zero)


G10 L20 ... refers to current location (eg if you touch off on a fixture or work piece)


P1, P2 .... P9 refers to the 'P' word in the above commands and correspond to G54, G55 .... G59.3

So
G10 L20 P2 X0 Y0
would set the G55 00 at the current location, right?
Neat!

Yes, that is the command used by all those 'touch off' features in a gui.