It is the adhesion between layers that has to be overcome, not the gravitational effect.
Can you suggest an experimental setup, that would be improved by low-gravity environment?
One of the techniques is the attempt to create the one atom strong layer using cvd: https://www.acsmaterial.com/blog-detail/cvd-graphene.html
I envision maybe making sheets of graphene from some kind of liquid suspension, but I have no idea if that's possible or, if it can be done, whether it's the best option. Can such an allotrope of carbon be assembled in such a way?
Meanwhile, in a magazine I have lying around there was an article about a serendipitous discovery of nanomachines that can walk unidirectionally along straight lines (as if on train tracks) on a plate of copper when subjected to a bit of electrical excitation. They're able to push things around, and so act like bulldozers. I ran across the article soon after I first ran across this discussion, and wondered if graphene could be constructed atom by atom on a copper plate using these nanomachines. The researchers are in Austria, I think, and I forget what they were actually trying to do with their experiment, but it wasn't anything to do with nanomachines.