It's been a while, but I wanted to let you know that your suggestion got me started in the direction that I needed.  I've now got all of my WebDialogWindows from individual pages working as if they were part of the MasterPage, outside of the splitter.

Rather than using document.body as the destination, I actually set up an empty div and did the appendChild to it.  When the WebDialogWindow closes, I reversed the copy so the element gets returned to its original location.  This was to address having multiple WDW on a single asp.net page.  I suspect that I could have left everything in the MasterPage div, but I have not tried it.

Thanks again,

Dave

Hi Dave,

If you do not use iframes (or Target/ContentUrl) or containers of dialog, then you may try to make initial state for dialog invisible, process initialize event, move html element of dialog to another parent like body and show dialog. Below is example.
Note: similar action is beyond support and if that "move" will trigger negative side effect, then it should not be used.

<script type="text/javascript">
function initDialog(dialog, evtArgs)
{
  var elem = dialog.get_element();
  elem.parentNode.removeChild(elem);
  document.body.appendChild(elem);
  dialog.show();
}
</script>

<div style="position:absolute;left:200px;top:200px;width:300px;height:300px;overflow:auto;background:cyan;">
  <ig:WebDialogWindow ID="WebDialogWindow1" runat="server" Width="300px" Height="300px" Modal="true" WindowState="Hidden">
     <ClientEvents Initialize="initDialog"></ClientEvents>
  </ig:WebDialogWindow>
</div>

<div style="position:absolute;left:300px;top:300px;width:300px;height:300px;overflow:auto;background:orange;"></div>