Utility to move or permanently delete a tag from a dataset

Realizing the potential complexity in this, we've had some instances where a utility that allowed us to move a tag from one dataset to another would be beneficial. Linked tags can help here but being able to move a tag (or list of tags) could be helpful. 

Another helpful tool along this same line would be an option to permanently delete a tag from a dataset. While obsoleting is helpful, there are times when I think full deletion and reduction in used disk space would be beneficial. Similar to the options for renaming, maybe an option where one could select a file (date) and choose to delete from that and older or that and new files would be helpful. That way if we had a tag that wasn't reporting right until a certain point, we could delete the incorrect history.