Losing nesting when editing a page

I was having the same trouble as my ‘Parents’ selector was only showing top level pages so as soon as I was on a child of a child page it reset the parent on save as it was not in the list. After much googling, I used this function this in my theme’s functions.php file:

add_filter( 'page_attributes_dropdown_pages_args', 'so_3538267_enable_parent_depth' );
add_filter( 'quick_edit_dropdown_pages_args', 'so_3538267_enable_parent_depth' );

function so_3538267_enable_parent_depth( $args )
{
    $args['depth'] = 2;
    return $args;
}

which I adapted from here: https://stackoverflow.com/questions/3538267/wordpress-admin-show-draft-pages-in-page-attributes-parent-page-dropdown

and this is the original function:

add_filter( 'page_attributes_dropdown_pages_args', 'so_3538267_enable_drafts_parents' );
add_filter( 'quick_edit_dropdown_pages_args', 'so_3538267_enable_drafts_parents' );

function so_3538267_enable_drafts_parents( $args )
{
    $args['post_status'] = 'draft,publish,pending';
    return $args;
}

If you do a var_dump($args); in the function and refresh or go to an edit page, you’ll see the options you can set.

Hope that helps