@NarnM Have you launched the game once since reinstalling it? The Sims 4 folder in Documents\Electronic Arts is only created when the game loads for the first time; the Mods folder is inside of that.
@NarnM You're looking inside the wrong Electronic Arts folder. If you launch Sims 4, there will be one inside Documents, and inside that will be a Sims 4 folder. The game couldn't even open if it couldn't write to this folder, so it has to be created.
If you can't find the Sims 4 folder in Documents\Electronic Arts, that means it's either in a different location than where you're looking, or it's being moved after the fact. For the former, make sure you're in the local version of Documents, not the one in OneDrive. You can see the file path above the list of files and folders. To open local Documents, click This PC in the left panel of a File Explorer window, then C > Users > your username > Documents.
If you still don't see a folder there, open the game, create a save (no need to spend much time on it), save your progress, and exit to the Main Menu rather than quitting. Click the Load Game button, choose your save, and hover over the folder icon with the other save info. Please copy the file path down and paste it into a reply here. You can write [username] instead of your actual username if you want, but let me know if the username you see is NOT the one associated with your main Windows account.
@NarnM If the game is reading the Sims 4 folder on D, as you've listed, then you probably used a symbolic link or redirected Documents to D without using a subfolder. Either way, the Sims 4 is looking for all your user content on D, not only the saves. So try putting your mods in D:\Electronic Arts\The Sims 4\Mods.
Edit: I just saw your new thread and merged it with your existing one. Please list the default location of Documents on your computer. Open a File Explorer window, right-click on Documents, select Properties > Location, and list the file path you see there.
I don't know where you read that the Mods folder only works on C. That's not technically correct: the Mods folder only works if it's inside the Sims 4 folder the game is reading, and that folder is on C by default. For you however, the folder is clearly on D.
