The action bar at the top of the Navigation pane contains buttons that control the content of that pane.

Like most navigation or directory trees, a plus symbol (+) to the left of a folder name indicates that the folder may be expanded to expose subfolders one level down, by clicking the plus symbol . Click the minus symbol (-) to collapse the subfolders again.

In the Content pane, an up arrow also means that a topic is expandable to show more information. Likewise the down arrow can be used to collapse the line.