title: NSToolbar segmented control like finder
body: <p>I'm updating and older macOS Application using newer NSToolbar feature like using <code>NSSearchToolbarItem</code> instead of manually creating it by setting the view of <code>NSToolbarItem</code> to <code>NSSearchField</code>.
  Currently the same is done for a <code>NSToolbarItem</code> containing a segmented control -&gt; <code>NSToolbarItem</code> + custom view.</p>
  <p>I've seen finder has the feature that the segmented control collapses if the toolbar wouldn't fit all the items anymore. How can i get this behaviour?</p>
  <p><img src="https://i.stack.imgur.com/8pj2n.png" height="50"> --&gt; <img src="https://i.stack.imgur.com/JY1im.png" height="50"></p>