At the bottom of the editing pane is a small tab labeled as As Diagram. The concept is that a UML diagram can be displayed in a number of ways, for example as a graphical diagram or as a table. Each representation would have its own tab and be selected by button 1 click on the tab.

Earlier versions of ArgoUML did implement a tabular representation, but the current release only supports a diagram representation, so this tab does not have any function.