How to convert your NieR:Automata PS4 save game to a PC compatible save game:
1. Export a decrypted save file with Apollo Save Tool from your PS4. There's plenty of tutorials on how to do this online. Make sure you export the one called GameData and not the one called SystemData.
2. Click on "Upload Save File" and pick your GameData file. The converter will automatically convert your save file to be compatible with the PC version of the game.
3. Download F-SERVO and import one of your old save files (located at \Documents \My Games\NieR_Automata\). Copy your Steam ID from that file, then import the converted file, paste in the Steam ID and save it.
4. Now you can simply put the converted file in your save directory and launch the game.
Credits:
Arthur Heitmann for helping figure out the offsets needed for the file to work on PC. RUGMJ for helping with the javascript code.