not able to access variable names

Modified the template to have a button in the lightbox (which leads to a form)

But cannot echo out the current photo url
so I could add it to the url (and the form could catch this)

In fact I can not access any of the items.. title, id, url …

is there a way or even a workaround.. ? This seems pretty simple, but the complexity and structure of this plugin prevents me of grasping where I could add this myself. so any help is welcome.

https://ww.wp.xz.cn/plugins/simple-lightbox/