I like this answer from one of the Redux co-authors:
https://github.com/reactjs/redux/issues/1287
Use React for ephemeral state that doesn’t matter to the app globally
and doesn’t mutate in complex ways. For example, a toggle in some UI
element, a form input state. Use Redux for state that matters globally
or is mutated in complex ways. For example, cached users, or a post
draft.Sometimes you’ll want to move from Redux state to React state (when
storing something in Redux gets awkward) or the other way around (when
more components need to have access to some state that used to be
local).The rule of thumb is: do whatever is less awkward.
That is, if you’re sure that your form won’t affect global state or need to be kept after your component is unmounted, then keep in the react state.