I need some help with moving the login screen to my primary display which I prefer as the left display
The ability to configure which monitor slick greeter appears on is only available on the version what is in 18.10
You could perhaps install the slick greeter version available in the linux mint repositories (sorry don’t know where they are) … or recompile the slick greeter from 18.10 under 18.04 … or use another lightdm greeter that has that ability … again not familiar with other greeters.
Just to check though… in menu - displays you have specified which is your primary monitor?