Archiving exercises is a great way to clean up your published Library.
You can only archive your exercise when there is submission data associated with it (A Learner has interacted with the Exercise). You cannot delete an Exercise that has submission data.
To archive your Exercise please do the following:
Go to the Library page. Select the downward facing arrow associated with the exercise you would like to archive.
From the drop down menu, select Archive.
Your exercise is now archived. You can now find it in the Archive section of the Library.