Duplicating lists is useful both for creating templates and for quickly creating new lists.
To duplicate an existing list, click the list name above the list to open the list options menu and select "Duplicate."
You can also access the list actions/duplication form from the sidebar by clicking the
v icon that appears as you hover your mouse above any list.
With the duplication form open, name the new list and choose whether or not to duplicate and reopen its completed tasks as well.
Click "Create New List" to begin the duplication process.
The duplicate copy of the list will appear above your other lists in the sidebar until the process is complete. You'll know it's finished when the spinning animation beside the list name disappears.