Sonos Playlists aren't listed on the switch

The Sonos Favourites list on the switch reflects the items shown in the desktop Sonos Controller app:

In most cases, content can be added using the phone app via "Add to My Sonos". However, this is not possible for adding Sonos Playlists. To add Sonos Playlists, choose "Add to Sonos Favorites" from the drop-down options to the right of the playlist in the desktop app: