This function allows you to toggle the toolbox's visibility on the dashboard designer canvas. 

You need to navigate to the Manage—Dashboard page. 

Choose a dashboard from the list and select the Actions—Design menu option. The dashboard content appears in the design view on a new page. To switch the display, click the Actions—Toolbox menu option. 

The toolbox is hidden, as shown below. You need to repeat the action to display the toolbox.