I asked thisthis question about what "the thing on the windscreen of some Piper aircraft is". It came out that it is used as small anti-icing.
The user Jules asked following in a comment of an answer:
Is de-icing this small an area generally beneficial for longer flights, or is it "just good enough" for a landing at the nearest airport if the ice buildup is starting to seem hazardous? (Asking as a non-pilot)
I also think it's a good question, but unfortunately the author of the answer didn't answer.
Thank you!