Inkline

Did you ever end up finding a solution. Exact same issue here. $message doesn’t seem to have a value inside the filter, although the filter does fire.

Your plugin works great for Posts or Custom links added to a WP menu, but does not work for Pages added to menus.

To fix…

Line 42 in submenu-filter.php is originally:

$item->slug = sanitize_title_with_dashes($item->post_title);

When you add pages to a WP menu, they don’t have a post_title property.

Simply change to use the ‘title’ property since all object types added to a WP menu have this property.

New Line 42:

$item->slug = sanitize_title_with_dashes($item->title);