Add custom fields to p2p admin box using p2p_candidate_title

I’ve been trying to add custom fields or additional meta data next to the candidate connection title.

function append_author_to_candidate_title( $title, $post, $ctype ) {
	if ( 'subdishes_to_groceries' == $ctype->name && 'subdishes' == $post->post_type ) {

		$title .= "ANYTHING";
	}
	return $title;
}
add_filter( 'p2p_candidate_title', 'append_author_to_candidate_title', 10, 3 );

Even with a static value, I get nothing. I’ve added this code to my functions.php.

I’ve also tried using custom fields with the default_cb key but even that does not seem to work. Please see following code:

p2p_register_connection_type( array(
    'name' => 'subdishes_to_groceries',
    'from' => 'subdishes',
    'to' => 'groceries',
    'title' => 'Sub Ingredients',
    'admin_box' => array(
        'context' => 'normal'
    ),
    'fields' => array(
        'yield_unit' => array(
            'title' => 'Y Unit',
            'type' => 'text',
            'default_cb' => 'get_groc_y_unit', // CALLBACK
        ),
        'yield_price' => array(
            'title' => 'Y Price',
            'type' => 'text',
            'default' => 'asdasdasd',
        ),
        )       

) );    

function get_groc_y_unit( $connection, $direction ) {

    global $post;
    $key = ( 'from' == $direction ) ? 'p2p_to' : 'p2p_from';
    $post = get_post( $connection->$key );
    setup_postdata($post);

    return the_title();

}

Am I missing anything, can anyone help please?