After I little digging I found the right action in the parent theme. The function looked like that (actually exactly the example I linked above):
//////////////////////////////
// Add page category filter //
//////////////////////////////
add_action('restrict_manage_posts', 'uncode_page_filter_post_type_by_taxonomy');
function uncode_page_filter_post_type_by_taxonomy() {
global $typenow;
$post_type="page"; // change to your post type
$taxonomy = 'page_category'; // change to your taxonomy
if ($typenow == $post_type) {
$selected = isset($_GET[$taxonomy]) ? $_GET[$taxonomy] : '';
$info_taxonomy = get_taxonomy($taxonomy);
wp_dropdown_categories(array(
'show_option_all' => sprintf(esc_html__("Show All %s", 'uncode'), $info_taxonomy->label),
'taxonomy' => $taxonomy,
'name' => $taxonomy,
'orderby' => 'name',
'selected' => $selected,
'show_count' => true,
'hide_empty' => true,
));
};
}
add_filter('parse_query', 'uncode_page_convert_id_to_term_in_query');
function uncode_page_convert_id_to_term_in_query($query) {
global $pagenow;
$post_type="page"; // change to your post type
$taxonomy = 'page_category'; // change to your taxonomy
$q_vars = &$query->query_vars;
if ( $pagenow == 'edit.php' && isset($q_vars['post_type']) && $q_vars['post_type'] == $post_type && isset($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;
}
}
Solution
To remove them I added a simple remove_action() to my child-theme function.php.
/**
* Remove page_category filter and parse query
*
**/
remove_action('restrict_manage_posts', 'uncode_page_filter_post_type_by_taxonomy');
remove_action('parse_query', 'uncode_page_convert_id_to_term_in_query');