For more complex use cases, Taxonomies might be useful https://discuss.flarum.org/d/30499-flamarkt-taxonomies
You can't nest taxonomies, but you could name them like breadcrumbs (Country > Region1
, Country > Region2
). The validation count being separate from the one from tags gives more flexibility.
You could probably use the breadcrumb approach with tags too.
A problem with the breadcrumb naming is that you can't easily filter the discussion list by intermediate labels. Currently in Taxonomies a single value can be selected at a time in the filter but this could be changed to allow selecting multiple values at once. It's possible to select multiple values by typing them manually in the URL separated by a comma.