This tool lists your Hypothesis tags, and enables you to rename one or more of them. If you have many annotations to search, it'll take a while to build the list. You can shortcut that process by specifying a particular tag you want to rename.
To see all your tags, increase the max to a number greater than your total # of annotations.
Please do make a safe copy your annotations first. And proceed with care. There a way to lose information without any technical malfunction. Suppose you are using three tags, A, B, and C, to classify annotations into three buckets. Then you rename B to C. Now bucket B is gone. There is only A, unchanged. and C, which includes what was in B. You can't reverse the arrow of entropy and reconstitute the set of annotations that were in B! More Hypothesis tools.