Visibility Public/Private

you may be able to create a custom field in the form builder, in my example it’s called “post_status”, then give it a selectable value, like “private: which triggers a conditional in the post template to update the status in for the post.

untested..

<?php
(get_post_meta($post->ID,'post_status',true) )
if($value=='private' {

// Update post
  $my_post = array();
  $my_post['ID'] = $id;
  $my_post['post_status'] = 'private';

// Update the post into the database
  wp_update_post( $my_post );
}
?>

something is wrong with that, but I tested with this and it worked.

<?php $your_custom_field = get_post_meta($post->ID, 'poststatus', true);
if ( $your_custom_field == 'private' ) {

// Update post
  $my_post = array();
  $my_post['ID'] = $id;
  $my_post['post_status'] = 'private';

// Update the post into the database
  wp_update_post( $my_post );
}
?>