Narrowing down filters

I think I am trying to do the same thing as described in this post, but not sure, so I will do my best to explain:
https://wordpress.org/support/topic/using-multiple-select-boxes?replies=3

I have two drop down boxes with category filters.

The left shows only job categories. When someone picks a job category, it displays only posts in that job category. Then, they can further narrow down the list by using the drop-down box on the right, which contains a list of US states.

On the Admin side, right now I use the “individual” option and select these categories manually but this doesn’t work well because the job categories and jobs within each state changes a lot. Sometimes categories have posts in them, and sometimes they don’t. If a category has no posts in it today, I can’t add it to the list, but it may have posts in it tomorrow.

I was hoping that selecting the parent category would allow child categories to show up in the filter whenever they have posts in them, but it seems that child categories need to be selected individually. It seems that if the user adds a new job category, it won’t show up either even if the parent is already in the filter.

Am I doing something wrong? If this is available on the Pro filter that is fine, just let me know.

Thank you1

https://wordpress.org/plugins/filter-custom-fields-taxonomies-light/