Dragging levels

In the Hera screenshots, it shows levels being dragged in the Scenario Editor. This doesn't seem to work in b6. Is there a special key combination that has to be pressed to drag the levels around?
This is the screenshot: (url="http://"http://www.AmbrosiaSW.com/news/upcoming/images/hera_1999_12_4.gif")http://www.AmbrosiaS...a_1999_12_4.gif(/url)

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