Wp Editor on Metabox - attempt 4

// for pages use 'edit_page_form' as the first parameter. And see my comment below.
add_action( 'edit_form_advanced', 'my_meta_editor' );
function my_meta_editor() {
// set 'your_meta_key' to the actual key

$content = get_post_meta($post->ID, 'att_meta_bio', true);
// only low case [a-z], no hyphens and underscores

$editor = 'mymetaeditor';
// See my comment below

$editor_settings = array(); wp_editor( $content, $editor, $editor_settings); }