Move completed tasks to a different calendar

Use case - I have a small 5-15 min task scheduled for later. But in my break/free time, I notice I can get the task done soon. So, I get the task done earlier than it's scheduled time.

I then mark task as done in Morgen. But since it is added to my calendar, my calendar apps will still give me the notification for it on it's scheduled time, and that will be annoying.

A feature to automatically shift completed tasks to another calendar, that my calendar apps don't show can solve this problem.

It will keep my main calendar app (Apple Cal, Google Cal) neat as well, as I don't want to see my completed tasks in the calendar, as there will be too many of them. I would only like to see the tasks I have not done.