@Override
		public TreeItem createItem(String tagName, @SuppressWarnings("rawtypes") Hashtable atts,
				HelpSet hs, Locale locale) {

			try {
				return doCreateItem(tagName, atts, hs, locale);
			}
			catch (Exception e) {
				Msg.error(this, "Unexected error creating a TOC item", e);
				throw new RuntimeException("Unexpected error creating a TOC item", e);
			}
		}
Our custom factory that knows how to look for extra XML attributes and how to 
create our custom tree items
Ghidra/Framework/Help/src/main/java/help/CustomTOCView.java