@sallomaa Sims 4 will always look for the user data, including saves, in Documents > Electronic Arts > The Sims 4. If you move this folder somewhere else, for example to your external drive, the game will create a new folder in the same location. The only way to move this folder is with a symbolic link. Here's how:
https://crinrict.com/blog/2020/02/moving-windows-documents-folder-to-external-drive-via-symbolic-link.html
If the command to create the symlink doesn't work, please use the exact file path rather than %userprofile% as written in the guide. You can see the exact file path by right-clicking on the Electronic Arts folder and selecting Properties > General, then looking for the Location.
If you're not sure what you're looking at, please list this location and the location where you want your Sims 4 folder to be on the external.