Your idea from the previous thread was a good one. Creating a new user, and using that as a model to restore from. If you have a back-up that you can use. Let's say, that you make a change using a GUI interface. After, making the change, you could bring up a shell session and use the find command to note all of the files added or updated. E.G.
find ~/ -cmin -10
If you make a note of what was changed you could restore these files from your previous backup. At least using the find command this way, you can learn where the settings are changed.