We just released 8.2.0 build 31229 which removes enforcement that the fullscreen resolution has to match a monitor mode reported by the OS.
This will allow power users to manually modify the GxFullscreenResolution CVar to whatever they want. Keep in mind, if you get the aspect ratio wrong, things will be very squished/stretched. If you’re running at a lower overall resolution, you’ll probably want to make sure the render scale is set to 100%. These steps should work on Mac and Windows.
I’ll give in game steps first and the the config file steps after.
In Game:
In the chat window, key in
/console gxFullscreenResolution "2560x1440"
with whatever resolution you want and then
/console UpdateWindow
to finalize the change.
From Config File:
To turn this on, open your Config.wtf file in a text editor. The default path is:
C:\Program Files (x86)\World of Warcraft\_retail_\WTF\Config.wtf
or
/Applications/World of Warcraft/_retail_/WTF/Config.wtf
Find or add GxFullscreenResolution in that file, with the resolution you want. Example:
SET GxFullscreenResolution "2560x1440"