MultiWorld Config File
This is the default MultiWorld Config File :
But you can enable or disable worlds with commands, take a look here
#This is the LavaBoat+ config file for worlds. #Define your worlds in which LavaBoat+ is enabled below: world=true AnotherWorldNameHere=true
For add new worlds type the next Line NameOfYourWorld = true if you want LavaBoat+ will be enabled in this world and change the true into false for disable LavaBoat+ in this world.
After editing this file you have to reload your server or restart it.