R – Adobe AIR custom chrome L-shape

I'm just going to give you the blunt answer: No.

The best way to handle this is to make the main class a subclass of Application instead of WindowedApplication, and set the initialWindows visible setting to false. Then, in your main class you create as many Window instances as you want.

Main class:

<Application xmlns="http://www.adobe.com/2006/mxml">
  <applicationComplete>main()</applicationComplete>
  <Script>
  <![CDATA[
  private function main( ) : void {
    var window : Window;
    for ( var i = 0; i < 5; i++ ) {
      window = new Window();
      window.width  = 200;
      window.height = 300;
      window.open(true);
    }
  }
  ]]>
  </Script>
</Application>

App config:

<application xmlns="http://ns.adobe.com/air/application/1.5">
  ...
  <initialWindow>
    ...
    <visible>false</visible>
  </initialWindow>
</application>