Welcome back, glad to see you've kept your head (and 'phones) above water!
Wow, what a storm.
I figured it out: in any Qobuz app (desktop, mobile, or web), after favoriting the playlist I can search for more tracks and add them to that playlist, just as if it's one of my own playlists, via each track's ellipsis (three dot) menus. Also I can remove tracks from the playlist via their ellipsis menus. But that's about it.
When I added my suggestions and removed the cover versions previously there, I found I couldn't move the added tracks to the same places in the playlist. They are just added to the bottom. So to get the same order again, I'd have to re-add all tracks in that order.
In that way they are matching Tidal and no better. Also at one point I had to log out and back in just to get the Playlist to update. Not sure how other services work, but at that point I decided this is no fun and not worth the trouble.
@Pro-Jules