Using this for hierarchical tags?

Hello, I have a blog where I talk about writing and different historical subjects. When I post articles, I use the side column to assign tags and categories so that visitors can more easily find particular subjects. I have been trying to find a plugin that will allow me to change the default tag cloud widget into one where I can list things hierarchically, such as a category being a particular subject, and if clicked on, it would do a drop down of sub-categories (from the tags). Is this plugin something I can use for that? Thanks!

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