In the official examples we have several top-level directories:
components
for “dumb” React components unaware of Redux;containers
for “smart” React components connected to Redux;actions
for all action creators, where file name corresponds to part of the app;reducers
for all reducers, where file name corresponds to state key;store
for store initialization.
This works well for small and mid-level size apps.
When you want to go more modular and group related functionality together, Ducks or other ways of grouping functionality by domain is a nice alternative way of structuring your Redux modules.
Ultimately choose whatever structure works best for you. There is no way Redux authors can know what’s convenient for you better than you do.