Force Keynote to move “this” object and not “that”

In Keynote, to arrange one object to another, I open the Inspector sidebar, then click the Format tab, then click Align, and then select, for example, Center or Middle or Left etc.

Object A stays in place and Object B moves. And here is my question: How is it possible to tell Keynote which one of these two objects is Object A and which one of them is Object B? That is, how to force it to move “this” object and not “that”?

I tried, example, the following approach. Select one object, then hold down Shift or Command key, then click another object. But it doesn’t solve the issue: Keynote continues to move the object which I would prefer to not move.