JED 1.6.0+ - Void dimension with forced Creative mode

{
    "dimensions": [
        {
            "dim": 8,
            "dimensiontype": {
                "id": 8,
                "name": "Void World",
                "suffix": "_dim8",
                "keeploaded": false,
                "worldprovider": "WorldProviderSurfaceJED",
                "require_exact_match": true
            },
            "worldinfo_onetime": {
                "generatorName": "flat",
                "generatorOptions": "3;minecraft:air;127;",
                "GameType": 1,
                "DayTime": 6000,
                "GameRules": {
                    "doDaylightCycle": "false",
                    "doWeatherCycle": "false"
                }
            },
            "jed": {
                "ForceGameMode": true
            }
        }
    ]
}