In the Settings menu (Windows+i keys), search for “Notifications” or, if you’re already looking at Focus Assist, choose “Notifications & Actions” from the left-hand menu. In addition to Focus Assist, there are Outlook notification settings available in Windows.
This is useful if you want Focus Assist turned on only at certain times of the day or just weekdays and/or weekends. You can additionally customize “During These Times” by clicking on it and changing the time options.