I want to create an agent with two flows using the new version of Dialogflow (CX), in some ways this 2 flows are very similar. That's why instead of creating from scratch all the pages of a flow i was looking if it was possible to copy and paste a flow and then make some changes!
That is not possible. However, in Dialogflow CX intents can be reused, which would speed up your progress as compared to Dialogflow ES. Additionally, you can create Route Groups to deal with Routes that should exist at multiple parts in your conversation tree. That should take care of some duplication!