The anatomy of Quick Add Child

admin.js

(function ( $ ) {
	"use strict";

	var post_ID = $('#post_ID').val(),
		parent_id = ( '' == $('#parent_id').val() ) ? 0 : $('#parent_id').val(),
		addNew = $('.add-new-h2'),
		html = '';

	html += ' <a id="add_new_sibling" href="post-new.php?post_type=' + typenow + '&parent_id=' + parent_id + '" class="add-new-h2" target="_blank">' + quick_add_child_js_params.add_new_sibling + '</a>';
	html += '<a id="add_new_child" href="post-new.php?post_type=' + typenow + '&parent_id=' + post_ID + '" class="add-new-h2" target="_blank">' + quick_add_child_js_params.add_new_child + '</a>';

	$(html).insertAfter(addNew);

	if ( quick_add_child_js_params.hide_add_new == 'on' )
		addNew.hide();

}(jQuery));

dropdown-args.php

<?php

$dropdown_args = array(
	'post_type'        => $post->post_type,
	'exclude_tree'     => $post->ID,
	'selected'         => $post->post_parent,
	'name'             => 'parent_id',
	'show_option_none' => __('(no parent)'),
	'sort_column'      => 'menu_order, post_title',
	'echo'             => 0,
);