Thanks.
Work fine with 2 tabs (one for Artist view, one for Album Covers view)
With 1 tab (Artist view -> double click an artist picture -> Album Covers view), The Album Covers view have no header.
Another bug:
(-> = double click // <- = mouse navigate back button)
Artists view grouped by Artists/First Letter -> Album Covers View <- Artists view grouped by Artists/First Letter
Now I want Artist view grouped by Album Artists/1st letter-> Album Covers View <- Artists view grouped by Artists/First Letter (and not Album Artists)
You have to restart MusicBee each time you switch between Artists/AlbumArtists/Composers