Move a reminder to another list on iCloud.com
When you move a reminder to another list, the change appears on all your iOS devices, iPadOS devices, and computers that have iCloud Reminders turned on.
Note: If you’re using upgraded reminders, you can’t move a reminder to another list on iCloud.com. You must use the Reminders app on a device with iOS 13, iPadOS, or macOS Catalina 10.15.
In Reminders on iCloud.com, select the list that contains the reminder you want to move, then select the reminder.
Click Details, click the List pop-up menu, then choose a different list.