In order to define a contextual action for FK windows, you need to put your Python script in your Python directory under a directory called Contextual_F_K_Display_Window.
Go to Tools->Options->Environment->Python Scripts (or Tools->Options->Python->Scripts in INTViewer 5.2) and click "Refresh from Disk". Your script should be listed automatically.
You will now be able to execute this script from the contextual menu of the FK window (note: there are 2 FK layers in this window):
This script will create a combined window of the reference layers and the fk layers contained in the FK window, and then close the FK window.
This script is attached to the bottom of this article.
The result after the script executes should look something like the following.