Don't think the idea is bad at all. Then you directly have a small dirty edge and could still use the railing for kitchen utensils or decoration. Knocking out the stone would of course be even nicer...
Unfortunately, chiseling off the stone is not possible. The windows are already firmly installed and sealed, the exterior window sills are in place, and everything inside is plastered...
Unfortunately, I also have no idea how to fix the problem, but I had to smile just now because EXACTLY the same thing happened to us. I know this doesn't help you now, but I am also curious about any further ideas.
Unfortunately, you can't knock off the stone. The windows are already firmly installed and sealed, the exterior window sills are in place, and all the interior surfaces are plastered...
So what? Who messed that up? If it was the company, they have to make sure it gets fixed. Then they should come up with a solution. Or was it already recorded incorrectly in the floor plan and the companies executed it correctly?
Don’t you have a construction manager to address this with? If he is a good one, he will have a good solution ready.