WP Admin Sort Custom Post Type Taxonomies Dropdown Replace function names, post type and taxonomy name and put in functions.php of child theme – https://pippinsplugins.com/post-list-filters-for-custom-taxonomies-in-manage-posts/
// Sortera bland titeltyper i månadsmail
function add_taxonomy_filters() {
global $typenow;
// an array of all the taxonomyies you want to display. Use the taxonomy name or slug
$taxonomies = array('titeltyp');
// must set this to the post type you want the filter(s) displayed on
if( $typenow == 'manadsmail' ){
foreach ($taxonomies as $tax_slug) {
$tax_obj = get_taxonomy($tax_slug);
$tax_name = $tax_obj->labels->name;
$terms = get_terms($tax_slug);
if(count($terms) > 0) {
echo "<select name='$tax_slug' id='$tax_slug' class='postform'>";
echo "<option value=''>Visa alla titlar / typer</option>";
foreach ($terms as $term) {
echo '<option value='. $term->slug, $_GET[$tax_slug] == $term->slug ? ' selected="selected"' : '','>' . $term->name .' (' . $term->count .')</option>';
}
echo "</select>";
}
}
}
}
add_action( 'restrict_manage_posts', 'add_taxonomy_filters' );