The "Global tags" words do not seem to appear under "Edit Tags" or in your library for those items, I noticed that too. Also, you are correct that you cannot untag those words. (Please Post a Suggestion in that sub-forum if you feel this behavior needs to be changed.) The tags that appear in your library can be called "Your tags"... meaning the tags that you added. But if you search in your art library for that pre-tagged-word (the "global tags" of the item), the item comes up, right?