title: The button that allowed seeing two file side by side is now disabled in Xcode
body: <p>This is how it looks like</p>
  
  <p><a href="https://i.stack.imgur.com/yKGLe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yKGLe.png" alt="enter image description here"></a></p>
  
  <p>Now I'm using Xcode 11.1. </p>
  
  <p>Everything was ok until I messed around with the project files, I guess. Also this feature works for the other projects but not with this one. How should I fix it?</p>