Unfortunately, this is the area where I found myself stumped.
I have an extended attribute for Elements which is a string that contains a resolvable URL to a published glossary, separate from the element definition which is set in the comment's section.
Under the "itemDecl" section for Element, I'm wanting to extend it, or possibly the "extendedAttributesDecl" to include this specific item in a comment in the XML output. I guess it's really a two part question, 1) How do I interrogate the extended attributes of an object with GTL and 2) what %variable% would display the results?