Tag management is definitely a place where we could add a few interfaces IMO; however, the crux behind adding them is more downstream than immediate. When a tag is created, there is the notion of someone using that tag (for whatever reason), and when they apply that tag to a piece of content/place/person, and start to bolt that into their daily productivity, it is difficult to insure that any actions taken to "merge" or "delete" tags will not have negative downstream affects of people not finding content they are used to. In a way, this is how categories add a lot of value (but I digress).
Currently, the best way to browse tags is via the Popular Tags Widget in each container and/or the global tags page: (/tags)
For example: https://community.jivesoftware.com/tags
Hope that helps, but definitely share your thoughts on what/how you'd like to see this done moving forward in the Jive Platform products space:
Hope this helps,