The pop-up Navigator is pared-down version of the Navigator Palette, available in pop-up form at the right edge of the Tab bar. You can use this instead of the Palette to save screen space.
The pop-up Navigator contains the Project Map, View Map and Layout Book (but not the Publisher).
Access Pop-up Navigator
•click the icon at the right end of the Tab Bar
•or click Ctrl/Cmd + Shift + N
Use the Chooser pop-up to show or hide the Navigator palette and related dialogs: