How to set an experience as a "What's new" based on the user former version?
You can specify experiences to specific users that have a certain version. If one user has a version 1.0 and never returned to the app, he/she would not need an experience that says, "We have fixed all the bugs." That user can receive an experience explaining all the new updates from the app.
You will need to specify exactly which former version you would like to send the experience to.