Add-ins are only loaded when Showcase starts up and cannot be unloaded while Showcase is running. There are two methods of
            controlling the loading of add-ins: 
         
         
            - By placing the add-in source file (.py) in the Showcase preferences directory which is where the userPrefs.xml file is located, (E.g. C:\My Documents\Autodesk Showcase 2012). 
            
- Via the add-in manager, accessible from the menu at File > Add-in Manager. The add-in manager tracks the add-ins in a file called plugins.xml which is in the same directory as userPref.xml.