You can merge the two items into one by selecting both (the small circle in the top-left of the poster when you hover over it) and then choosing “Merge” from the “More” menu at the top-right of the screen. I believe you’ll need to be in the “Library” view of your library to do this.
Just keep in mind @OttoKerner 's advice here; Plex will retain the view history (and other metadata) from the item which is selected first.
