I like your thought process, truly!

But the reality is even in very very LEO, the amount of actual space means it'd have to be a literal cloud of material up there to block enough solar energy. And that would actually be worse as while you're reflecting the energy, you're also creating a blanket and we make plenty enough heat down here already.

Your idea has merit, but the semi-better idea kicked around in that regard is to make a more 'permanent' cloud or such at LaGrange point 1, always in between the Sun and the Earth, permanently (until we decide to remove/reduce it) blocking the amount of solar energy to ease the warming issue. There's no additional blanket of material to keep energy in, so the Earth cools naturally over decades. Yes, decades.

But then, people would just use the opportunity to make even further ways to warm up the Earth, then we'd send more stuff to block sun, and it's then a runaway situation where we wind up actually causing an ice age...

Meaning at the end, we just should fix it right, today, on the 'ground' if you will, and not use tricks elsewhere we'll just screw it up with anyway because humans, amirite?

Also, astronomers won't like it, all that junk already gets in the way and they don't want it to be a thing (Starlink, OneWeb, etc), so there's that.