Hello,
1) Check the permissions of our FTP user, we can’t edit file https://prnt.sc/11p57u1
2) I see that the default WooCommerce widget https://prnt.sc/11p611l also displays Uncategoried in the list https://prnt.sc/11p64lt even if Hide empty is checked.
So, I think you need to solve this issue with the WooCommerce support team https://wordpress.org/support/plugin/woocommerce/ first and then reply back and we’ll proceed with the search.
3) Do you add the CSS code to child theme style.css? Do you add CSS code after the existing header https://gyazo.com/27a687df58b5f79b07cb3a16dcef480b or instead of this?
Regards