Hey Soruud,
You would be better off putting future posts in the Mach 4 General Discussion and not here in the Mach 4 Toolbox.
But, I can answer your question on displaying the G90 or G91.
Open the screen editor and place a DRO anywhere you want to display G90 or G91.
Set the DRO's Parameter to 4003. This will link it to the register that holds the value of the G90 or G91.