Lagrange L1 is basically the only place you can place something between Earth and the Sun without heavy maintenance costs to maintain the position. L1 is at 1%

Lagrange L1 is basically the only place you can place something between Earth and the Sun without heavy maintenance costs to maintain the position. L1 is at 1% of the distance from earth to the sun. This means that if you are going to put something reflective there, there is basically no benefit size-wise compared to doing it directly on earth. (Diagrams usually make it look like it's 1/3 of the way, which would have a 77% increase to the covered area). Feels like it would be easier to put something reflective like that somewhere on earth instead, allowing for a much bigger coverage per $.