Even though there are already 2 other questions on the subject (this and this), no documentation have yet been provided by somebody from Sonos developer team.
The problem still remains: how one can attain a similar customised Spotify-like display type on Sonos mobile controller app. I'm talking about the root container of the Spotify music-service. It looks like this.
whereas the documentation clearly only talks about the grid, list, hero and editorial display types, none of which being the one used in Spotify music-service integration. Take a look:
The above 2 other questions I mentioned indicate that, as of April '18, Sonos developer team was working on enabling this experience, but, after almost 2 years, there is nothing AFAIK.
Thanks for help!