Show admin column for custom taxonomy

To enable admin columns for custom taxonomies, all you have to do is to add ‘show_admin_column’ => true when registering a custom taxonomy:

register_taxonomy('kb_tag', null,
    array(
        'label' => 'KB Tags',
        'show_admin_column' => true // this is the relevant line
    ));

In total it is:

add_action('init', 'wpkb_add_kb_taxonomies', 9);
function wpkb_add_kb_taxonomies()
{
    register_taxonomy('kb_tag', null,
        array(
            'label' => 'KB Tags',
            'show_admin_column' => true
        ));
    register_taxonomy('kb_category', null,
        array(
            'label' => 'KB Categories',
            'show_admin_column' => true
        ));
    register_taxonomy('kb_target', null, 
        array(
            'label' => 'KB Targets',
            'show_admin_column' => true
        ));
}