Hmmm. Haven't seen that question asked before. Unless someone comes up with a better answer, I suppose you could achieve this in the following way:
1. Create and name your "base" World State.
2. Export that World State to the cloud (not sure if it's available yet, but I think it might be ...)
3. Make the one or two changes you want and rename the World State.
4. Export the amended WS to the cloud.
You wouldn't have both World States saved in the Tapestry but, logically, they'd both be available for importing into the game from the cloud.
Just my initial thoughts. If you get a better/easier answer, by all means go that route instead!