From the main menu bar: View, Toolbars, put a check next to Outlining
That should do it.
If you like the old Outline view better than the new "squeeze it into a pane"
approach, you can also do this:
Main menu bar, choose Tools, Customize
Click to the Commands tab
In the Categories list, click View
In the Commands list, locate the Outline icon and drag it to any toolbar you
like.
Click Close
Now you can click your new Outline button to go into the original full-screen
Outline view