Custom taxonomy admin page

Not sure why I didn’t think of this earlier. I suppose I was hoping for a way to ‘hijack’ the default page to display something else… Anyway following my original method:

If you want a custom admin page for a taxonomy, you can set ‘show_ui’ => false when you register it to suppress the default admin page and then create a new admin page to replace it.

You can get round the issue of edit-tags.php?taxonomy=taxonomy-slug taking you to the hidden taxonomy page, by simply redirecting the user to your page, using wp_redirect:

add_action('load-edit-tags.php','myprefix_redirect_to_custompage');
function myprefix_redirect_to_custompage(){
    $screen = get_current_screen(); 
    if($screen->id == 'edit-mytax'){
        $url = admin_url('edit.php?page=mypage');
        wp_redirect($url); 
        exit;
    }
}

Assuming mytax is the taxonomy name. $url should be the url of the custom page replacing the default taxonomy page.