Looks like the actual media (image/video) in the lightbox element is not editable in the CMS editor, only in the designer? The only way to access the actual media file or link is to use a collection. Is this a bug or feature? 
Hey Christoffer,
Iām running into the same problem. I am not a coder / scripter, but I understand the language somewhat. So with some help from Google Gemini I got something working.
This should be possible better in terms of scripting, but this will help me now.
Hopefully there is someone in the community or at Webflow who would like to pick this up. It would be nice if customers who use the Editor could also process the content themselves.
I also placed the Editor Control icon in a different location, because with a large hero banner it sometimes falls out of view.
Hope this helps you and that there is someone who wants/can improve this.[https://preview.webflow.com/preview/lab-2024?utm_medium=preview_link&utm_source=designer&utm_content=lab-2024&preview=69762b97f5146a8e152eb94d8553072a&workflow=preview]
So the extra fields you see are not shown when the site is LIVE, but they are when the Editor is active.
This way, someone can still adjust the Media link of the LightBox via the Editor.
Here the same website live: https://lab-2024.webflow.io