todos-thunk.tsx

export default function Todos() {
  const items = useStore(state => state.todos.items);

  //    👇 
  const save = useActions(actions => actions.todos.save);

  const [newTodo, setNewTodo] = useState("");

  return (
    <div>
      ...
      <button onClick={() => save(newTodo)}>Add</button>
    </div>
  );
}