this is fully depends on your WM. First of all, you can just bind scrot on any key combination your WM allow to.
Second of all, say, KDE's Spectacle can be used to take screenshot by timeout. So, you set timeout, press "take screenshot", it hides it's window, you open your popup menu, wait for timeout, and get a screenshot containing your popup menu without pressing any hotkeys ;)
signature.asc
Description: This is a digitally signed message part.
