The above snippet acts like a normal WordPress-Taxonomy, but i encountered a bug. You have to have at least one Tag-Taxonomy-Metabox on the Edit-View to have the js-functionalities (expand the most used, add,…) working. Btw. if someone is interested in my final implementation:
public function create_field( $field ) {
$this->set_field_defaults( $field );
$terms = get_terms($field['taxonomy'], array('hide_empty' => false));
$value = $field['value'];
$arr = get_taxonomies(array('name' => $field['taxonomy']), 'objects');
if($arr[$field['taxonomy']]->hierarchical) {
post_categories_meta_box(get_post($num = get_the_ID()), array('args' => array('taxonomy' => $field['taxonomy'])));
} else {
post_tags_meta_box(get_post($num = get_the_ID()), array('args' => array('taxonomy' => $field['taxonomy'])));
}
}
(From Line 172)
Greetings Maik