Step 1
Open the File Explorer on your computer and go to the following directory:
C:\Users\[your username]\AppData\Local\Packages\CoffeeStainStudios.DeepRockGalactic_496a1srhmar9w\SystemAppData\wgs\
Step 2
Inside the wgs folder, there will be a folder with a long combination of letters and numbers. Open this folder.
Step 3
Inside this folder there should be another folder with long combination of letters and numbers. Open this folder.
Step 4
Inside this folder, you will find a file that consists of a combination of letters and numbers. This is the save file you want to transfer to Steam. Copy this file to the desktop.
Step 5
Go to the following directory:
C:\Program Files (x86)\Steam\steamapps\common\Deep Rock Galactic\FSD\Saved\SaveGames
Step 6
Rename the save file on the desktop to match the name of the 01234_player.sav file in the SaveGames folder. For example, if the 01234_player.sav file is named 43210_player.sav, you should rename your save file on the desktop to 43210_player.sav as well.
Step 7
Copy the file _player.sav on the desktop to the SaveGames folder.
Step 8
Start up Deep Rock Galactic on Steam and your save file should just load up.