Sometimes the default SharePoint 2013 Quick Launch is not enough to assist users to navigate to a SharePoint site. The tree view is an extra navigation option that provides a hierarchical view of all sites, lists and libraries in the site, including any sites below the current site level, such as the Document Center site template, display tree view navigation by default.
Do one of the following:
1. On the SharePoint site, click Site Settings
2. In the Look and Feel column, click Tree View.
3. Do one of the following:
- To show the tree view, select the Enable Tree View check box and then click OK.
- To hide the tree view, clear the Enable Tree View check box and then click OK.
If you want to display only tree view navigation, clear the Enable Quick Launch check box. If both the Quick Launch and tree view navigation are enabled, the tree view navigation will appear underneath the Quick Launch. Now you can see the Tree view instead of Quick launch.
4. Now you can see the Tree view instead of Quick launch.