You are unable to edit mods within the Documents folder

[TheCreamCheeseWonton]

If you manually download mods to your documents folder, or create mods through the EU4 "Create Mod" function in the EU4 Game Launcher, you can not select those mods.

[mmyers]

What is an example of a mod folder that the editor does not pick up? In games.txt, you can see the path inside Documents that the editor expects to find mods in:

eu4 = {
    inherit = dw
    display = "EU4"
    text = yaml
    has_lakes = yes
    view_set = eu4
    new_style_mod = yes
    mod_path = "Paradox Interactive/Europa Universalis IV"
}

This would be inside your Documents folder, as noted in the comment at the beginning of the file. So in my case I have a mod in C:\Users\MyName\Documents\Paradox Interactive\Europa Universalis IV\mod\TestMod and the editor is able to find and use it.

[TheCreamCheeseWonton]

For some reason, using this exact same setup detailed in your response, using a fresh install of the editor only allows you to select mods that have been manually downloaded to your install folders /mod folder.

[mmyers]

The log file (output.log) should explain where it is looking for mods. What does it say when you start the editor?