Having a menu named "Navigation" that does not actually provide any navigation is confusing to users and doesn't make any sense. This menu doesn't provide very much value, and has been removed.

As part of this change, the "node/add" menu item was moved into the management menu by default.

All modules in core that provide links should add them into the "Primary navigation" or "Administration" menus instead.

Introduced in branch: 
1.0.x
Introduced in version: 
1.0.0
Impacts: 
Architects, Administrators, Editors
Module developers
Theme developers
Related Github Issues: 
https://github.com/backdrop/backdrop-issues/issues/224
https://github.com/backdrop/backdrop-issues/issues/127
https://github.com/backdrop/backdrop/pull/447