Super happy for this community. I was able to solve the problem by supporting the cactus with a cardboard tube, to essentially push it forward in order to grow in front of the ledge... my supports won't hold in wet weather, but based on how fast the cactus is growing it should be "trained"...

I didn’t anticipate this cactus getting so huge when planting it years ago, and now it is so tall it is about to hit the ledge above it. What can I do?