In SharePoint Online 2013, in the Promoted Actions toolbar among Share, Follow, Edit, Sync commands, there is another command called Focus on Content.
What it does?
- when activated is closes the left panel (the one with the picture, recent documents, navigation links, etc.
More exactly, it closes the left Navigation Pane for the current page.
If we exit the page and the Focus on Content is On, when we return to that page, the Navigation Pane will still be closed.