Because I had duplicates into my unlimited Playlist of ROON, I decided to delete it entirely in view of import my 3 full (2000) Playlists of QOBUZ again.
Very bad surprise : my manipulation had deleted my QOBUZ Playlists too !!!
Fortunately, I had imported my QOBUZ Playlists on a hard drive on my PC. In “Local”, I retrieved my Playlists. The problem is that when I want to reconstitute “My Playlists” from my imports, it create copies of the Playlists but they are empty.