Not sure if this applies to Spotify, but I’ll create my playlists in my Amazon app, that I can then access anywhere, including through Sonos.  If you create a Spotify playlist in the Spotify app, can you not see it in the Sonos app?  If not, can you use Spotify connect?

This is how I do it with Spotify: Spotify playlists are shared with Sonos, but not vice versa.

Greatly appreciate your insights. Going forward, it sounds like creating a playlist within Spotify or Amazon is the way to go. Unfortunately, for me, I have over 3000 songs in my Sonos playlist (created using Spotify over a period of months). It sounds like I would have to go through the time and trouble of creating this extensive playlist again through the Spotify app. I’m hopeful that someday soon Sonos and Spotify will be able to link accounts.

I’m wondering if there is a way to upload my Sonos playlist to Spotify?

iOS App Store… Phonos Plus.

https://support.soundiiz.com/hc/en-us/articles/360018717099-Export-Sonos-playlists-and-transfer-them-with-Soundiiz

I downloaded the the free version of the Phonos Plus app on my MacBook Air but am struggling to find  how to export my Sonos playlist. Can I export using the free version? Or does this require a premium subscription?

Contact the developer and ask.

I would be very surprised if it is possible to export from Sonos. Sonos playlists are stored on the Sonos speakers, not in the cloud. And Sonos playlists may consist of tracks from multiple sources, including locally stored tracks.

It is NOT correct to say that a Sonos playlist has been created in Spotify. A Sonos plqylist that consists entirely of Spotify tracks has still been created in Sonos 

I would give up trying to export a Sonos playlist to Spotify because I think it's a doomed exercise.

I would be amazed if that changed in future