This question was posted in response to the following article: http://help.adobe.com/en_US/robohelp/robohtml/WS355AEF7F-34ED-4124-BC8F-B27DE7A228E1.html
I don't find a "Default Window Menu" in my webhelp layouts.
There isn't one so I'm not surprised
You create windows for WebHelp and generate. You determine the window to use in the call of the help. When you call the help using the API you can optionally provide a window name and then RoboHelp uses the window you defined. (The API is something your developer will use.)