Flutter Stepper focus view on header of stepper on step change

Question

I have Stepper where every Step is dynamically build after opening. Steps are various, once they height is less than 1/2 of screen height, another time Step have 2x of screen height. As I said previously, widgets inside steppers are build automatically using FutureBuilders widgets, so Stepper could change his height realtime.

I try do it using FocusNode and force focus on first element of each Step, but my solution is not working every time. How to force move of screen scroll to beginning of current opened Step? It means that title of current Step should be just below Scaffolds AppBar.

Of course my widget stack looks like this:

Scaffold
ScrollView
Stepper
Step (with header and buttons)
step content: Column (with form widgets and a lot of Text widgets)