I believe that by default at installing MusicBee the navigation panel is hidden.
Personally I feel it would be much better if it was visible by default.
It's a too important part of the interface to hide by default, especially hiding it from new users.
And, for experienced users who like lean and mean, it's easy to hide it at their desire.
New users will have a hard time finding that this 'navigator' panel even exists or find out how to have it showing.