When i develop iOS app with Xcode, i design the user interface by edit the Main.storyboard file. But when i click the Main.storyboard file to edit it, i can not find the View Controller Scene (Document Outline) panel at center editor left side. This confused me a lot. Finally i find the solution to fix it.
In below picture, we can not find the View Controller Scene panel which is also called Document Outline.
You can click the Xcode menu item Editor —> Document Outline to make the View Controller Scene panel visible.
When you click above menu item to check it, you can see below picture, the View Controller Scene is displayed, when you click above menu item again to uncheck it, the View Controller Scene will be hided.
Besides above method, you can also click the expand icon () before the View as: bar that is located at the bottom of the center editor to display or hide the Document Outline panel.