The best way to visualize this would be the same format as the map’s are already. A view where you can build a story map from your existing story map’s. Like this you would just need a top level item witch has the epics from the different maps as child’s. Like this you could see all your items as well as the planned releases. By any changes on this map you could use the settings from the single map and change it there. This would even add a new Level of planning as you could visualize even relations over more then one map and coordinate all the project’s / teams.
