New
#11
Actually the OP was unclear. In their thread title they said 'active window' but they later said, ".. except for active windows only." Windows is plural, and so I cannot determine if they mean ANY open windows or merely ONE open window.
Greenshot can provides two different ways to achieve this. One is a keystroke --
and one is a sort of hunting with your cursor to select the window you want.
I concur with your comment that said request is a no. I'm attempting to offer a fairly similar yes but I need the OP to answer my question.