Can the Sun be used as a point source of light to achive better focus? There's a limit to how well sunlight can be focused by a parabolic reflector or a lens because the Sun is not a point source. I wonder if the sunlight could be engineered to work as if it was (much more similar to) a point source.

If almost all of the Solar disc was covered by a coronograph, the light which gets through a small hole would be (almost) a point source. Is that correct?

If then an array of such covered reflectors or lenses concentrated their light to one and the same point, would a better focus be achieved than without covers?
No, it won't work. After all, it is recommended to make a pinhole camera to watch a solar eclipse. What you suggested is similar to a pinhole camera. Why it won't work, is that the rays that pass through the pinhole are not parallel, but divergent. Light from a point source would have (nearly) parallel rays.