I need just exactly what you have here, but unfortunately there are a few things that don't work.
I have a Woocommerce shop where you can buy printer equipment. So I have a main category and 2 sub categories. One with the series, one with the actual printer. Since I want to show only the printers in the category list on the product page I didn't add it to the main and first subcategory. When I click on the manufacturer it shows a 1, that's ok. But on the series subcategory there is always a 0 even though there are products.
But the main problem is that the link doesn't work. When I chose all the categories it goes to the shop page and not to the chosen product.
By the way I'd love to translate the plugin to German, but haven't done something like that before 😉 maybe we can get in touch?