The drain should be centered on the floor, so between the wall and curb. The valve can go wherever you want it, and has nothing to do with the drain.

I agree with catbuilder. The valve can be anywhere. Ours is going to be just inside the shower so you can turn it on easily before you get into the shower. Then we have the slide bar centered on the shower wall to the right of the valve.

Nothing even says it has to be centered - and there are different styles of drains like linear and hidden. You just don't want to be standing on it.

I centered valve with the drain. If I was clever. I would have tried to center it with the sliding shower door.

But I didn't. It looks fine. To each its own.