I was working on a script and after a computer restart, my script was no longer listed in the DisplayFusion scripts list. Where are the scripts stored? Is it possible to edit them or copy the files outside the built in script window?

View or backup scripts is not so simple, because they are stored in the registry.
But you can save the program settings. Yes, this saves all the settings, including functions(scripts). To do this, go to "Settings" and click on "Export Settings".

You can use Notepad or any other you liked editor for the external editing. I use SublimeText and lately [URL =https://code.visualstudio.com/]VS Code[/URL] with C# for VS Code and gist extension. Video tutorial how to install VSCode and C# ext

Is this true?! Are the scripts stored in the registry? If so this is super bad!