title: Editing Build Settings in xcode 4
body: <p>I have been unable to work out how to edit build settings using the pop-up shown below.</p>
  
  <p><img src="https://i.stack.imgur.com/TAxBc.png" alt="enter image description here"></p>
  
  <p>I can enter multiple lines in the pop-up by clicking the '+'.  My questions are :-</p>
  
  <ol>
  <li>What is the checkbox next to the setting used for?</li>
  <li>Once I have entered one or more settings in the pop-up, how do I make them transfer to the setting I am editing.  There isn't a 'Save' button, and clicking off the pop-up closes it but doesn't seem to save the entered data.</li>
  </ol>
  
  <p>Thanks </p>