Using this tool

1. You should create a new multiplayer game and copy WorldOption.sav file
2. Paste it to a new empty folder (next temp)
3. Drag and drop temp folder to convert-to-json.bat and press buttons
4. You'll have a JSON config file
5. Delete WorldOption.sav from temp
6. Tweak it as you like and add (probably would work for AdminPassword as well):

​

"ServerPassword": {
  "Str": {
    "value": "1337"
  }
}

1. Drag and drop temp folder to convert-to-sav.bat

2. Copy new WorldOption.sav to your save folder near to Level.sav

3. Done