title: Add buttons to Mac window Title Bars, system-wide
body: <p>I want to be able to add a button to the <a href="https://developer.apple.com/design/human-interface-guidelines/macos/windows-and-views/window-anatomy/" rel="nofollow noreferrer">title bar</a> of <strong>all windows that open on a Mac</strong>.</p>
  
  <p>The button will go on the right hand side, opposite the <code>X - +</code> buttons.</p>
  
  <p>This is asked about windows of <em>my app</em> here:<br>
  <a href="https://stackoverflow.com/questions/24023000/how-can-i-create-yosemite-style-unified-toolbar-in-interface-builder">How can I create Yosemite-style unified toolbar in Interface Builder?</a></p>
  
  <p>But I want the button to appear on <strong>all windows, of any app, that are opened on the Mac</strong>. Obviously, this will only happen once the user has installed this program.</p>
  
  <p>I understand that this is essentially "plugging into" the OS's UI, but I have seen other apps do this, which makes me feel that it is do-able.</p>
  
  <p>Here is screenshot where I want the button:</p>
  
  <p><img src="https://i.stack.imgur.com/1OjLR.png" alt="Screenshot"></p>