You were right. It works just like you said. So everyone on version 6.12.10 should update to their version of choice, that way you can set multiple cores and edit the MacOS VM without getting the „Guest has not initialized the display (yet)”. Thank you @avinyc
I have the same version of unRaid and i encounter the same problem. I followed the tutorial and deleted de nvram files and it does not work. I tried many things but if i change even the icon from the VM xml it wont boot anymore giving the "Guest has not initialized the display yet" error.