I have read before that there is nothing in place to select this in WordPress, but digging into the WordPress database there is a field called _thumbnail_id, and all that happens is WordPress populates this with the corresponding attachment_id of the image you want as the Featured Thumbnail i.e. http://your-website.com/wp-admin/media.php?attachment_id=727
So in this instance 727 is the attachment id and putting this in the _thumbnail_id makes that the Featured Thumbnail, so my question is: Is there a way in Mars Edit to get WordPress to report back what the attachment_id is ???