No, but you’re right that there isn’t an obvious way.
All the current ways to create a tag are associated with putting the tag to use (attaching it to a new topic, adding a tag as a synonym to an existing tag, creating a tag while creating a tag group). Beyond this, I believe the only other way to create a new tag is through bulk upload.
This has been discussed a bit in Create tags outside of new post — I don’t think there’s any opposition to this feature, it just hasn’t been prioritized.