You can duplicate an assignment at any stage: inactive, active, or archived. The duplicate created will always be an inactive assignment.
Along the top ribbon, click Assignments.
Select the Inactive, Active, or Archived tab.
On the assignment you'd like to duplicate, click the three dots.
Click the Duplicate assignment option.
A new assignment page will open with all the details from the original assignment. Make any edits you'd like to the new version.
When you've finished, click Save for later or Activate assignment. Your new assignment is now under the Inactive tab, ready to share with students anytime.