If you sign into your livexlive account online and perhaps check there, I assume they may show up in favourites, but if no answers are found, you can apparently contact/ask their Support via the link below:

https://support.liveone.com/hc/en-us/requests/new

Where can I find the dislike button? I don’t think I’ve ever come across it before. 

It’s on the ‘now playing’ screen, see the image in the first post above.

Thanks, Ken.  I contacted LiveOne support (LiveOne being the company that provides the LiveXLive service) and they told me I could find the disliked song list in the My Station Ratings at the bottom of the Station’s page in the LiveOne app.  ...And true enough, it looked like the list I would be looking for, except that they were no songs in the list.  I checked that the feature was working as I thought it should, within the LiveOne app, but it appears that Sonos does not relay that info correctly to LiveOne (either that or LiveOne does not display it).

I could tell I was logged into the correct LiveOne account since the station appeared as the latest one played, among other familiar stations.

Yea I don’t see it. Is in in beta or a particular music service?

It’s part of the LivexLive service within the App.