All UI actions/views that need to be updated to support multiple content objects should also have a "single-slot" mode, triggered by providing the slot argument in the URL. With that argument set, the user would only see the content of a single slot for the view action, would be able to edit a single slot with edit action, etc.
See https://www.mediawiki.org/wiki/Multi-Content_Revisions/Views#Single-Slot_UI