Alfred,
I put new leather on my dash pieces about two years ago. The molded upper dash piece that this little screw goes through fits so tight that the screw isn't necessary. I didn't like the looks of the screw either so I never put it back in and nothing rattles. There are obviously other dash screws, but I suppose because of position this one bothered me about as much as the forward window pillar screws. Unfortunately, they had to be in place so I just don't look at them!
Tim Dunagan
1971 280 SL