There are many reasons you may want to create a duplicate copy of a saved list. The most common reason is to preserve the list's original criteria. By creating a copy you can modify the criteria of your new list and add or remove segments if desired. This will allow you to use the copy as a starting point for a new list.
From Your Saved Lists Page
From this page, you can select the three-dot menu option on the right hand side of the screen of the list you wish to duplicate. Once you select the three-dot menu option will be given a few options, at this point you can select Duplicate.
After selecting Duplicate, you will be asked to rename the list and click Create to move forward.
When Viewing Your List
When viewing your saved list, you can also create a duplicate copy from this page. To do so, select the first Duplicate List icon in the top right hand corner of the screen.
After selecting the Duplicate List icon, you will be asked to rename the list and click Create to move forward.