In order to move a content set between different Journeys, you must first make sure that the trigger type is the same as the one you are moving to. In this example, I want to move the content set "15% discount" to the lane/flow "Winback".
Click on the three dots on the email you want to move.
Click on "Move to".
Then choose which "Journey" you want to move to.
Then to which "Lane/Flow".
As you can see now, the email "15% discount!" is located.
