I had to restore my c drive (windows 10) with true image and after I lost my saves. I had 6 saves and then had only 2, because the saves were on the C: drive. I Install my games on my d: and J: drives. I want the game to save games on the same drive I installed it on.

Not sure if there's a way to change it in the game options. Since it's saved in the User folder, you could try moving the entire User folder onto a different drive (you'd have to do some fiddling with the registry, I think). You may be able to find instructions on how to do that via Google search. I don't recall all the details.

Another option may be to periodically copy the save games to a backup folder so you at least have them if something else happens.

I never said my c drive crashed! and I never have to reinstall windows. I image my drive with true image and every now and then I experiment with new programs that after I will reimage the drive back to when I started experimenting.
If you don't know what True image is, it is a program that will create a file that is an image of your c drive (or any other drive you want) and if you want to go back to a previous state of your windows you just restore the file. It's cloning your drive to a file. I have about 14 images of my c drive. I also use a 1tb ssd m2 chip for my drive. Problem is I will sometimes forget to backup the saves before I reimage my drive. This is why having the saves on my J: drive (where the game is installed to) would be best.

If you don't use GOG Galaxy with cloud saves or a save game manager then you could try Windows Junctions/Hard Links.

Create ELEX Save game folder on D: or J: e.g. "J:\SaveGames\Elex"
Backup your original "C:\Users\**USERNAME**\AppData\Local\ELEX\SaveGames" folder, just in case. I usually "Right-Click, Send To Compressed Folder" and copy the zip file somewhere safe.
Copy Elex Save files from "C:\Users\**USERNAME**\AppData\Local\ELEX\SaveGames" to "J:\SaveGames\Elex"
Rename or Delete the "SaveGames" folder in "C:\Users\**USERNAME**\AppData\Local\ELEX". I usually just put an underscore at the start so it becomes "_SaveGames" and is out of the way.

Open a CMD prompt as administrator
Enter this command changing **USERNAME** for your user/profile name:
mklink /J "C:\Users\**USERNAME**\AppData\Local\ELEX\SaveGames" "J:\SaveGames\Elex"
You should get a message saying the junction was created and some arrows showing there's a link between the two folders.

The folder in C: will have a shortcut symbol on it and in DOS it will be specified "<JUNCTION>" not "<DIR>".
I just tried it and it worked for me but i don't know how it will impact the Galaxy Cloud Backups but i suppose you don't use Galaxy to run ELEX. You can delete the link on C: if you need to and the folder on J: will be fine.
I also haven't checked if the Junction persists between reboots but i think it should. Hope it helps.