Thanks for the review!
Meta Slider did used to attach the slides to the slideshow using the 'post_parent' setup, but WordPress only allows for a 1:1 relationship between attached posts. That caused problems when people wanted to use the same image in multiple slideshows.
Since then the way slides and slideshows are associated has been re-jigged to allow users to attach the same image to multiple slideshows (posts). Meta Slider now uses a hidden taxonomy to maintain the relationships.
I would happily put something back in to show that the slides are attached to 'something', but it could be confusing if the slide is in fact associated with 2 or more slideshows.