My focus is RoboHelp rather than FrameMaker, but let me see if I can help. It sounds like you may have already found this, but just in case, there is this thread which seems related to what you are asking. That said, the string you use as an example seems to be proprietary to WebWorks.
Here is something I found on the Adobe Tech Comm Blog
Meanwhile, I will try to find some other resources.
Adobe Certified RoboHelp and Captivate Instructor
Thanks John, much appreciated. http://forums.adobe.com/thread/795893 seems to be the same situation for me. Though I am unsure what str=MapID means int he suggested solution. Our testing has included using the URL.htm#topicalias. Do we need to include the MapID numeral as wel? #topicalias=16
When I test using the CSH pod the correct page launches. So this seems to be a string syntax issue. I want the whole help system to launch though, not just the topic in a single pane. Is that a URL string element as well? I created a new window but the CSH test tool does not launch the page if I enter the window name.
The RH help for the test tool is not very descriptive http://help.adobe.com/en_US/RoboHelp/8.0/RoboHTML/WS5b3ccc516d4fbf351e63e3d11aff59c571-7fe 0.html
The #<str=MapID is the string that you need to append in your main help url to open the CSH page with map id = MapID (it will be alphanumeric string), but this is required if you want to directly call the CSH page in a browser.
Hope this helps and feel free to revert back for any clarification
For custom windows (defined in Help project), add ">" followed by the window name ("/help/help.htm>mywin") and it shows that you have missed the symbol ">".
All the elaborated help and support is there in the CSH API