Thanks for your comments, I really appreciate that.
I don’t think I can be much help in this case, though. The mashup queries are run using the WordPress ‘wp_query’ object (https://codex.wordpress.org/Class_Reference/WP_Query).
Other than ‘sticky posts’, I don’t wp_query really has any syntax for showing a category + specific post(s), and it’s not something I’ve built into the plugin.
Maybe a workaround would be to show two maps – a map of the current location and another mashup with the other category?