thanks for the answer but thats not the Problem I have. I will try to explain it with screenshots
Here I can choose Fullscreen (Vollbild). It's ok so far...
But when I have a composition and want to inside the lightbox, the fullscreen button is greyed out. I can't even scale the size of the image in the lightbox.
For lightbox does not work full-screen mode. It's only for slideshow mod. There is no way to make full screen lightbox using standard tools.
To scale the size isn't possible as well?