Thanks for the other two articles. I will look into those suggestions tomorrow.
But per your comment, “rename any duplicates of "iTunes Music Library.xml" or “iTunes Library.xml.” As I said, I searched every location possible for duplicates. As in the "iTunes Music Library.xml" or “iTunes Library.xml.” files and there is no duplicate of either of those files anywhere to be found.
And as I said, “I read, and tried the suggestions for ways of removing duplicated iTunes Playlists from my Sonos system.” which included re-indexing the Sonos library. I did that three times in hopes of it fully clearing out the duplicates. Actually, I even removed my NAS drive and the music library completely from the Sonos controller, re-indexed with it removed. And the Playlists were still showing. I renamed the Playlists in my iTunes. Removed the Playlists completely from my NAS drive. Exported my Playlists again to my NAS drive from iTunes and reconnected my Music library again to my Sonos. Once again, all the duplicates were still showing. I even tried completely removing, re-indexed, re-named, re-indexed again, re-installed, re-indexed a third time. The duplicates were still showing.
I feel I almost have to completely reset each of my speakers to clear these Playlists. But, why would I have to do that, when I was told before on the Sonos support, “you should never have to reset your Sonos speakers.”
As said, I’ll try the other link suggestions tomorrow. Thank you.
Perhaps see this support document and rename any duplicates of "iTunes Music Library.xml" or “iTunes Library.xml.”
https://support.sonos.com/s/article/4930
Don’t forget to also re-index your Sonos library
You may also find these two links helpful too:
https://discussions.apple.com/thread/251571845
https://audiophilestyle.com/forums/topic/24121-where-is-the-proper-location-for-the-itunes-libraryxml-file/