@ozkanpakdil: I have also considered the approach of displaying a screenshot. Though, that would also mean switching from screen mirroring in the live session to individual virtual screens for the still image on the beamer and then back again once the changes are done and the presentation continues. I suspect this would not go without both monitors going black as they do when performing theses steps manually.

I am looking for a seamless transition. My idea is to have some sort of still-image command for the graphics output. Like saying: freeze the currently given output and do not react to any changes.