If you have unlocked a dashboard and have entered the edit mode, you will see the Clone Dashboard Contents option so long as you have the group permission to Copy Widgets and Dashboards.

Choose the Clone Dashboard Contents option to duplicate the whole contents of the dashboard so that you can add the to another existing dashboard. When you click this menu item, the Dashboard Copy dialog window opens.

Enter a name in the Description field (optional) and the width of the dashboard or report and choose the type by selecting one of the radio buttons then click Create to generate the dashboard or report.