The viewer's Standard toolbar contains tools controlling basic study operations.
Show study list, 
Close study, 
Open next study, 
Open previous study, 
Bookmark current study, 
Restore book-marked study, 
By default, the standard toolbar is not displayed. To display the standard toolbar, select View/Toolbars/Standard Toolbar. All functions controlled by the buttons on the standard toolbar are available from the file menu, and in some cases using hot keys.