title: Qt designer: How to add widget to a layout in the designer when the layout appears infinitely thin?
body: <p>I am using Qt Designer, and I would like to move a couple of top-level widgets into a horizontal layout.</p>
  
  <p>I have dragged a "Horizontal Layout" object into the form.  I am now attempting to drag the desired widgets into the layout.</p>
  
  <p>Unfortunately, the new Horizontal Layout widget is infinitely thin:</p>
  
  <p><img src="https://i.stack.imgur.com/Tzhvk.jpg" alt="Infinitely Thin Layout"></p>
  
  <p>... and I cannot drag my "Import Progress" label widget or my progress bar widget into the new horizontal layout widget.</p>
  
  <p>Note that when I attempt to drag the desired widgets over the new horizontal layout widget, Qt Designer does not do anything useful for me in terms of expanding the drop region to make the horizontal widget available as a drop target.  So I'm stuck.</p>
  
  <p>How do I add widgets to an infinitely-thin layout widget in Qt Designer?</p>