Your thread is not titled.
By the way, I just realized you are new to ATP. So a big
to you. And so glad you found your way here.
I've never had to cut any of my tall sedum back, but I know that you can pinch them back when plants are about 8" tall, no later than mid
June. Pinch back to 4–6", leaving 2–3 nodes to produce lateral branching.
It will produce smaller blooms, the more blooms the smaller they will be.
Hope this helps.