I have two other inputs on this behavior that might trigger a thought (I hope). I just created a Smartlist to find duplicate files (- ~dup=[File Size],[Name]) as part of my occasional maintenance. Many of the duplicates found were, in fact, not duplicates, but the same files, listed multiple times because the song was in multiple playlists. I tried deleting one song of a pair of duplicates and both listings were deleted - obviously it was the same song listed twice, but when I deleted the instance that included the playlist it deleted the main instance too.
I also just searched for a particular file from the search box and it came up with six instances, all with the exact same Filename. Again, it is clearly one file (I did verify that via File Explorer just to be 100% sure) but listed six times. Four of the instances showed one playlist the song is in (all four were different playlists), one showed two playlists and one showed four playlists. Yes, that song is in ten of my playlists. See the attached image.
As I said in my original post this behavior of seeing multiple entries for a single file makes life difficult for me. I still want to see what playlists a song is in, but prefer to see that in a single entry, not having to look at multiple entries. If there is a setting that can turn the multiple listings off I would very much appreciate your ideas.