A full list of the labels that are in use for your manual are available in the label menu. To access this menu, simply click the label icon (the one that looks like a price tag) in the right side menu of any procedure.
The label menu is the same no matter which procedure it is accessed from, and shows all available labels, not just the few that are in use for that specific procedure.
You can also view the labels through the push navigation on the top left
From there, all the labels will be shown.
You can click on Manage Labels at the bottom