The Change Icon action allows you changing window's default icon (that one displayed both on the leftmost of window's title bar and window's corresponding taskbar entry) to the one you find more suitable.
Once applied, this action will automatically prevent the set icon from further changes which window's application may induce.
Hint You can change the default icon of any window to an icon of another application thus disguising target window's identity. You can also change window's icon to a unique one thus improving its identity, i.e. making it more distinguishable, pleasurable and easy to find.