Hey Adam,
I’m not 100% sure how you’d do this, unfortunately.
If you’re able to get help with the WP_Query parameters, we can integrate them into WP Show Posts, as it sets up a WP_Query instance.
It may be worth asking over on wordpress.stackexchange.com if it’s possible to bring those posts with a meta value to the top using WP_Query. If someone can point us in the right direction there, we can make it work in the plugin.
Here’s something I found, but I’m not sure it’s exactly what you’re looking for: https://wordpress.stackexchange.com/questions/278337/wp-query-order-by-multiple-meta-keys-fields