title: Describing Sub-activities with Call Behavior Actions
body: <p>I created activity diagram D1. Then I created element "behavior" in the diagram D1. I also created activity diagram D2.
  I choose Element Properties "behavior" link at the diagram D1.</p>
  
  <p>When I hover the mouse over the "<code>Confirm Order</code>" behavior and double-click on it to transition to activity diagram D2 ("<code>ConfirmOrder.activity</code>") nothing happens.</p>
  
  <p>What am I doing wrong?</p>
  
  <p><img src="https://i.stack.imgur.com/xILpq.png" alt="enter image description here"></p>