@alyjohn1234 I was also struggling with this, as I tried to create the folder manually and put the plist file in like I always did. Didn't seem to work. What eventually worked for me was following this: https://gist.github.com/ejdyksen/8302862 and rather using the adaugherity version of the script that they suggest to download instead. It's used to fix EDID problems on external monitors by creating a plist file in the Library Displays Overrides folder using your monitor's values. What I just did then was to edit the created plist file in a text editor, and then replace all the contents with the contents of the plist file generated by the comsysto interface, save as sudo, unplug and replug the monitor and then using RDM I was able to choose e.g. 1080p HiDPI resolution. I hope this helps.