Can we change the top image for a stack of photos?

[Couscous]

I created a stack of photos an original and an edited version. The original became the top of the stack, what I would see when scanning through my library. I wanted the edited one to be the top.
I can not find any place in the program to assign the top to a different photo.

I did figure out that the top photo is the first one I select when creating a stack, so I have to unstack and then re-stack them. This will be a problem later!

Is there a better way?