When creating an object in draft mode either by adding or cloning an existing one any many-to-many references are not displayed in the datamanager record view. No records are created in the pivot tables but the versioned pivot tables are populated with the property _version_is_latest_draft=1.
When editing the draft record the many-to-many properties are shown in the form but still won't be displayed in the record view.
Object Room allows versions and drafts and has a many-to-many relationship with Amenity via the versioned and drafts-enabled pivot table rooms_amenities. Create a number of amenities, then create a room as a draft and add amenities. When you then view the room the amenities won't be shown. If you edit the room you should see the amenities in the edit form. If you publish the room the amenities are displayed.