Extending a taxonomy in a context

We have created a taxonomy of regions (in which users live), used in the profile and a few other places.
But when we want to use regions for events, there are a couple of extra possibilities – an event might be nationwide or online. Is there any way of having these available in the region dropdown for creating events but not in the member registration form?
I would rather not create a separate taxonomy (there are a lot of regions) and don’t see how two separate taxonomies could connect when, for example, listing all events in a region?

Drupal version: 

Source: https://www.drupal.org/taxonomy/term/22/feed