Help search doesn't find "hidden citation"

This isn’t a suggestion for a new feature. Just pointing out the EN X7’s help had trouble finding a commonly used feature. In the how-to forum, a user wanted to have references in his/her bibiography that are not cited in the text. I searched for “hidden citation” and the first hit had what the user wanted. I then searched X7’s help. None of the hits had the information. See attachment.