Is your employee returning to your company on a therapeutic part-time contract ? It's not always easy to know how to indicate it in your schedule. For this, you have two possibilities:
The creation of an amendment could be a solution. By stating your employee's new weekly work time, you won't have to second guess yourself when you create your schedule. To create an amendment, you can read this article.
Another option is to schedule your employee for their work hours and indicate the rest of their contracted work time as "Sick Leave" by adding a new absence.