Converting drop down to text box

So I looked but didn't see a post on this so I thought I'd ask.

I have a request to convert the fandoms (categories) from a hierarchical dropdown (Movies -> MCU, Movies -> Wonder Woman, TV -> Merlin, TV -> Stargate Atlantis, TV -> Starsky and Hutch) to a text box.  Kind of like on Wordpress when you're going to add in a tag, you start to type in the tag name and it pulls it up.  Has anyone successfully done this?  I haven't, and just started looking into it, so I thought I'd ask before I get in and start futzing with things.

Thanks!

walter