dashiichi: Use F12, which saves the picture via the GoG overlay. It's saved to ~\Documents\GOG Galaxy\Screenshots\No Man's Sky. Wait for the menu block to fade by itself, leaving the glyphs behind. Of course you can also hide the menu + glyphs with LShift and then hit F12 for a stealth screenshot.
mbrowne: Thanks, but I'm not running Galaxy, so looking for other alternatives. The normal things should work, but they don't cuz any keypress brings back that menu thingie...
Plan B: Switch to borderless mode instead of full screen. That puts the display "on" the Windows desktop (sort of) and from there the Print Screen key should capture the image.
Just tried it. It does work ... sort of. It almost seemed like the captured image was one capture behind. I'd definitely have an image viewer handy to verify that what's in the clipboard is what's intended. Of course, since the clipboard is volatile you'd want to view and save it right away anyhow.
So, not as graceful as having an app automatically save the image to a timestamped file but with some cursing and questioning the ancestry of assorted Microsoft employees, it does work.