In other words, there is no need to use state management techniques
(ScopedModel, Redux, etc.) on this kind of state.
All you need is a StatefulWidget.

Below, you see how the currently selected item in a bottom navigation bar is
held in the _index field of the _MyHomepageState class.
In this example, _index is ephemeral state.

Here, using setState() and a field inside the StatefulWidget’s State
class is completely natural. No other part of your app needs to access
_index. The variable only changes inside the MyHomepage widget.
And, if the user closes and restarts the app,
you don’t mind that _index resets to zero.

App state

State that is not ephemeral,
that you want to share across many parts of your app,
and that you want to keep between user sessions,
is what we call application state
(sometimes also called shared state).

Examples of application state: