How to clone an island

gistfile1.txt

You create a new project in UEFN.
You close UEFN.
You navigate to the project you are cloning in File Explorer and copy the entire Plugins folder
Navigate to the new project in File Explorer
Delete the Plugins folder and paste in the Plugins folder from step 3.
Open the UEFNPROJECT in any text editor
Change the plugins.name from the new project's name to the name of the project you are copying
"plugins": [
        {
            "name": "OriginalIslandName",
            "bIsRoot": true,
            "bIsPublic": false
        }
    ],

Save the UEFNPROJECT file and close it.
Open UEFN and enjoy your cloned project
 
Credit for that technique goes to Wasti. He showed it to me in The Lab Discord.