i made number of tests and set or reset these options, run mpsetup and they where left intact. Are you sure you do not have other applications (in background) that reset them? You were right it happens also without the execution of mpsetup -> my fault 😂
Did you see the other left problems? (i edited my answer). I have listed them here:
(I don't want to be outrageous, but if these functions could also be implemented that would be awesome)
1) I found a problem which is the same as the problem i had before.
When the rectangle is higher then wide, the LISP gets confused again.
Is there a fix for this, because sometimes we have plans that are like 600mm wide and 900mm high.
(Like a fix where it checks: When the rectangle is higher then long it sets the layout into portrait mode)
2) It would be perfect if i would be able to set the plot options via the LISP.
Just like the option to choose the printer. So when execute mpsetup there would be a 5th choice (named
"Plotoptions") where a window pops up and i can select which options i want to be active.
(Picture to see which options i mean):

( 3) One more thing:
If the LISP cannot find a suitable paper size for a layout, it would be important that I get a message about it (a
window that pops up, not only in the console) and that nothing gets changed in this layout.
Currently the paper sizes gets a bit buggy and it gets really small (see in picture below).

) -> Saw your answer on that and tested it and it worked. Now also the white background doesnt change. Thanks!