I am looking to add this same functionality. We are trying to avoid using tags, to avoid duplicate content in our website, and since the Metafields will already be set, it would nice to be able to automate our category creation based on that. I am curious if you ever found a solution to this?
I am thinking of trying Arigato Automation, but we may end up on a plan where we will have Shopify Flow, and I am curious if Shopify Flow would do the same thing?
I also wondered if there might be some faceted searching apps, that would be able to create smart collections based on metafields, since there is a good chance we might need to add a more complex search system.