Hello,

You can open and customize the lightbox using the cursor (navigator).

Please follow the steps below:

1. Open the page with the YellowPencil editor.
2. From the right panel, select the cursor instead of the topmost Elementor Inspector.
3. Click on the item that opens the lightbox.
4. Then, reactivate the Element Inspector and edit the content of the lightbox.

For more information, please take a look at this article.

I hope this helps

Best regards