You can upload your own UI pages under "Configuration" -> "Files". These either replace existing ones or generate a link. If you only want to make the page available for one language, you can start the file name with the language abbreviation: de_variables.htm only appears if the language is German. If the file begins with user_ (after an optional language abbreviation), everyone can access this page, otherwise only the admin can.

Here you will find a sample file for a customised UI page. You can use this to display currently defined Charging Manager variables.