To create a new subscriber list that has the same list settings, fields and form designs as an existing list in your account use the Duplicate list feature.
When you duplicate a list of subscribers the list settings, merge tags or custom fields are replicated, so you don’t have to go through the same steps to recreate the original list setup.
The Duplicate feature allows you to choose to duplicate a subscriber list with or without subscribers.
To duplicate a list
Select the My Lists option from the List Menu. This will display all of your current lists,
Click on the Actions drop-down menu next to the list you want to work with and select Duplicate. This will open the Settings for Copy of the list window.
Name your new list and click Copy only list settings and fields or Copy list with subscribers depending on your needs.
Your new list will appear at the top of the page.