Filter WooCommerce admin products list by a custom taxonomy

There is some missing parts in your code:

Try the following:

add_action('restrict_manage_posts', 'admin_products_by_manufacturer_filter_dropdown');
function admin_products_by_manufacturer_filter_dropdown() {
    global $typenow, $pagenow;

    $taxonomy = 'vyrobca'; // The custom taxonomy

    if( 'edit.php' === $pagenow && 'product' === $typenow && taxonomy_exists( $taxonomy ) ) {
        $info_taxonomy = get_taxonomy($taxonomy);
        $selected      = isset($_GET[$taxonomy]) ? $_GET[$taxonomy] : '';

        wp_dropdown_categories( array(
            'show_option_all' => sprintf( __("Zobraziť všetkých %s", "woocommerce"), $info_taxonomy->label ),
            'taxonomy'        => $taxonomy,
            'name'            => $taxonomy,
            'selected'        => $selected,
            'orderby'         => 'name',
            'show_count'      => true,
            'hide_empty'      => true,
        ) );
    }
}

add_action('parse_query', 'admin_products_by_manufacturer_filter_query');
function admin_products_by_manufacturer_filter_query( $query ) {
    global $typenow, $pagenow;

    $taxonomy = 'vyrobca'; // The custom taxonomy

    if ( 'edit.php' === $pagenow && 'product' === $typenow && taxonomy_exists( $taxonomy ) ) {
        $q_vars = &$query->query_vars;

        if ( isset($q_vars[$taxonomy]) && is_numeric($q_vars[$taxonomy]) && $q_vars[$taxonomy] != 0 ) {
            $term = get_term_by('id', $q_vars[$taxonomy], $taxonomy);
            $q_vars[$taxonomy] = $term->slug;
        }
    }
}

Code goes in functions.php file of your active child theme (or active theme). It should works.