The current webmap version allows me to add a map image layer then create custom popups and arcade expressions then save them back to the map image layer's Json. It is important for users adding my authoritative map image layer to get the popup that I've created. The Map Viewer Bata has no such capability that I am aware of. Since the details page for a registered map image layer does not have a Visualization tab that allows me to build and save popups and expressions, this ability is very important part of the current webmap that should not be lost when the Beta version goes live. If there is a work around that I am unaware of, please let me know.
It would also be great to be able to save popups, expressions and symbology from Map Viewer Beta to a registered feature layer.
