The final two World nitro codenames were found at last:
https://www.nintendo.com/jp/games/switch2/aaaaa/assets/img/online-events/sticker/Sign_StormClouds.png
Great ? Block Ruins is StormClouds
https://www.nintendo.com/jp/games/switch2/aaaaa/assets/img/online-events/sticker/Sign_RaftingRiver.png
Cheep Cheep Falls is RaftingRiver