Have you tried the search option in GiD website?
You can use it to find any concept in our website, including the GiD manuals.
Just search for the command or option in GiD that you want to learn about. In the results page you will be able to filter the results by the location, such as user, reference and customization manual, or even in the GiD forum.
Just select the tab that you are interested in for improving your search.