Here is a new World my 9 year old son made using the Supreme with Cheese editor. It's the first time I have done this so I hope the link works. Please feel free to comment or rate the world... or just say you've played it!
To get this to work I think you need to copy the file into the Supreme Worlds folder. Go on FILE EXPLORER then LOCAL DISK then PROGRAM FILES (X86) then SUPREME folder then WORLDS folder (copy game add on file into this folder) and hopefully this new World should be on the SWC World menu.
Enjoy, Merry Christmas!!!