Since you can assing an timeline item to an individual or to a multiple users, set a timeframe and check it off; have you considered showing it as a notification in "Things to do"?
I agree with Adree. It would be super helpful if a person could be notified of assigned tasks in some form (either via email or through the To-Do list), rather than having to go through the entire timeline to see whether anything has been assigned to them. Thank you for your consideration.