Ah, okay, thanks for the tip!
That isn't listed among the hotkeys in the editor, though. I deliberately looked again this time whether I could fine anything along those lines
, since I overread the duplicate function (pressing C in the editor) just recently.
So the suggestion would then be to add "I: export level image as PNG" to the hotkeys in the respective menu of the editor. It is listed in the player as "Save image", but not in the editor.