Storyboard Entry Point Missing
Click on Top of ViewController or Controller in Document Outline window (on left side) of the Controller you want to make Storyboard Entry Point.
Click on Attribute inspector button (in right side).
Enable "Is Initial View Controller".
Storyboard Entry Point will reappear hopefully.
There is a Is Initial Controller checkbox in the Attributes Inspector (⌥⌘4 or ⌥⌘5) of the window controller in Interface Builder