This function lets you toggle the toolbox show/hide on the dashboard designer canvas. 

You should navigate to the Manage—Dashboard page. 

Select a dashboard from the list and click the Actions—Design menu option. The dashboard content is rendered in the design view on the new page. To toggle the display, click the Actions—Toolbox menu option. 

The toolbox is hidden, as seen below. You must repeat the action to show the toolbox like before.