djvm13 You can install the game's program files wherever you want, but NOT in Documents. If you'd rather install to D, go ahead. Just make a separate folder on D, for example D:\Games, and choose that when installing.
If you want to do a clean uninstall of Sims 4 before reinstalling, which might be a good idea if you've had the game installed in multiple locations, here's how:
📓[GUIDE] [PC] How to Clean-uninstall Sims 4 | EA Forums - 12636503
Note that all of this is separate from the user folder, which will be in Documents > Electronic Arts regardless of where you've installed the game. The mod manager should be working with this folder. If it's not, if it can't find the folder on D, then use a different manager or just manage the files yourself. Mod managers are not a great option anyway for various reasons.