I have experience with a Mori MV-40 with a Yasnac control.
Our control provides only 3 different work offsets, G54 G55 G56.
Coordinate values can be preset by the program or input manually by repeatedly pressing the "Settings" button until the work offsets page is displayed.
Use the absolute/relative toggle button to switch between INPUT/INPUT+ (Fanuc style). Cursor to the desired offset/axis, type the new coordinate value and press WRITE (Enter).
It's easier to DO than describe
To change these values through the program:
We'll input the coordinate values X+1.0000 Y-2.0000 Z-3.000 into G54.
Here's the block of program code:
N1 G10 L2 P1 X+1.0000 Y-2.0000 Z-3.0000
(Note: The 'P1' in line N1 references G54.
Substituting P2 would reference G55, P3 would reference G56.)
Now, we'll make G54 active and rapid to our new zero point
N2 G90 G00 G54 X0 Y0
All work offsets are referenced from machine zero.
Hope this helps...