Please help me find an assistant editor

There is no ViewController in the second screenshot. Why ? How did you create the app ? Which template did you choose ? What is the class of the ViewController we see in storyboard ? Is it a pure UIViewController ? Then you will have no specific code for it.

Otherwise,

• create a new File
• select Cocoa Touch Class, click Next
• Give a name to the class as FirstViewController
• it is subclass of UIViewController
• click next, then validate.

The class should appear in the left panel.

• Give this class to the ViewController (Identity inspector)
• Then option-click on FirstViewController in the left panel
• code will open on the right.

You tagged Swift playground. It does not appear to be a playground app.