View completed reminders in a list: Select the reminder list, scroll to the top of the list until you see Completed, then click Show.
View all completed reminders: Select the Scheduled reminder list, scroll to the top of the list until you see Completed, then click Show.
An app icon appears next to reminders you added from other apps.
If there’s an app icon to the right of the reminder name in the Reminders app Control access to your calendar and reminders on Mac