Get brand from taxonomy?

This plugin is pretty amazing but I’m having trouble with one thing: I’d like to fill the brand field in my Google Shopping Feed by using a taxonomy. Brands in my Woocommerce shop are a custom taxonomy with one value set for each product. This needs to stay a taxonomy for structural reasons. But the plugin only allows me to select custom fields so now I can’t populate the brand.

Is there an option for this that I’m missing? If not, is there a filter or action I can use to get the brand in there? Or else, does the paid version of the plugin provide for this? Hoping someone can point me in the right direction here – thanks in advance.