What is the A350's procedure for stained cockpit windows?
I am not sure if this applies to modern jets, but pilots of the past were sometimes landing "sideways" by using https://en.wikipedia.org/wiki/Slip_(aerodynamics). That provided some view from the side window.

I believe one example of that could be found in "Fate is the Hunter" by Ernest Gann.

Also general aviation pilots sometimes use this technique if the windshield is iced over.