I can see this is an old chestnut. But in 2021 it should NOT exist….
I am have enormous frustrations in deleting/editing the Sonos Library (Not playlist). I found I had a whole load of duplicates when I connected my WD My Cloud Home NAS. I have since edited the original library elsewhere…..deleted the folder pointed to on the NAS… but still Sonos “sees” the tracks and trys to play them. Disconnecting the NAS also deleting the WD service app and reconnecting and deleting the folder still fails to remove the Library.
This is a real error within the sonos software in not being able to edit/delete library content.
How can I tell Sonos to delete this library. I am sure when I reupload the Library to the NAS ot will see playable and unplayable tracks.. Making playing an album impossible