I’m afraid Sonos decided you didn’t need that capability in the new app (and they have also disabled plyalist maintenance in the app until about then so there’s no work-around) until they get round to implementing it in July (lots of discussion elsewhere on the forum). 

I suggest you switch back to the old v16.1 again using one of the APK mirroring sites (sorry, I don’t know how to do it on iOS). You can also use one of the desktop apps as they still work - the functionality is still available in your speakers, Sonos just chose to cut us all off from it.