I think you can just change lines 21 and 22 of your serverconfig.json
21: "SaveFileLocation": "/var/vintagestory/data/Saves/default.vcdbs",
22: "WorldName": "A new world"
to something else like this:
21: "SaveFileLocation": "/var/vintagestory/data/Saves/myWorld.vcdbs",
22: "WorldName": "myWorld"
The next time you restart the server should create a new world.
I hope I could help you