I'm looking at WWDC session 414 video "What's new in xCode" at about 29:00 into the video the presenter opens a "preview" panel in universal storyboard to see how an iPhone and iPad versions of the same storyboard would look side by side. The presenter used the same button typically used to select recently viewed files, scrolled to the bottom and chose "preview".
I would really like to try this feature, however I cannot find a way to open the preview panel in xCode Beta 3, how can I do this?