WordPress - Add private/draft/future/pending pages to parent dropdown when setting page parent in the Page Attributes/Quick Editor

weba_dropdown_pages_change_args.php

<?php

/**
 * Add private/draft/future/pending pages to parent dropdown when setting
 * page parent in the Page Attributes/Quick Editor
 *
 * @since 3.3.0
 *
 * @see wp_dropdown_pages()
 *
 * @param array $dropdown_args Array of arguments used to generate the pages drop-down.
 * @param WP_Post $post The current post.
 */
function weba_dropdown_pages_change_args( $dropdown_args, $post ) {
	$dropdown_args['post_status'] = array( 'publish', 'private' );
	return $dropdown_args;
}
add_filter( 'page_attributes_dropdown_pages_args', 'weba_dropdown_pages_change_args', 10, 2 );
add_filter( 'quick_edit_dropdown_pages_args', 'weba_dropdown_pages_change_args' );