I know how to filter posts in the admin view by taxonomy terms but in my case I'd like to be able to view posts based on whether they have a specific taxonomy (not its terms) attached.
For example: Post type is 'event'. There's two taxonomies - 'Regional' and 'International'. They both have their own terms and I can create two separate filters for them. What I'd like to have is a filter switch that would enable me to see events that are either 'Regional' or 'International'.
Could someone point me to the right direction? I'm fairly new to WP_Queries but I imagine I'd have to check if the post belongs to any of the terms of the taxonomy?