Can a User Create Tags?
Yes. Anyone who can tag an article can create new tags from the tag window, except in restricted categories. Hashtags can require a minimum role.
Yes. People who can tag an article can also create new tags from the tag window, when they publish the article or later. They cannot create tags in a restricted category, and the platform can set a minimum role for creating hashtags.
To learn how, read How to create a new tag?