My C:\ hard drive was almost full (only 8 GB empty space is left), so I wanted to relocate the C&C3 stuff from it (323 MB savegames). However, as far as I know, the save game folder is hardcoded to be C:\Users\{your username}\Saved Games\Command & Conquer 3 Tiberium Wars\{Profile name}
So I used Junction (https://docs.microsoft.com/en-us/sysinternals/downloads/junction) to redirect that folder to the other hard drive (it had 38 GB empty space).

NOTE 1: the tutorial of the website is incomplete and somewhat outdated. On 64-bit operational systems, you have to use junction64.exe and the command will look like this:
junction64 "C:\Users\{your username}\Saves games\Command & Conquer 3 Tiberium Wars\{Profile name}" "new folder somewhere else"
(without parentheses, spaces in the folder names cause problems)

NOTE 2: in my example, I only redirected 1 profile because I had no more. If you have lots of profiles, this method becomes troublesome. Maybe redirection of the "Command & Conquer 3 Tiberium Wars" folder is more efficient, but I did not test it.

I hope this post was not completely useless. By the way, since 2006, were there more professional solutions for this problem? For example, hex editing the EXE file itself or some other less hardcore stuff?