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?
I figured it out - rather than trying to show preview for the current storyboard, you need to open a copy of the storyboard in the assistant editor, then click on the "' button in top left and select preview. This leaves the original storyboard on left and opens preview in place of the duplicate storyboard that was opened in the assistant editor.