To "duplicate" a list, you can simply make a second list of the same contacts. First, run a filter with the criteria "Lists," "is on all of the following Lists [your data entry list]."

Then you can add everyone from this filter to a list, by clicking on Actions in the upper right hand corner, selecting "Add all to list," naming that list in the "+ Create list" section, and pressing the yellow, "Create" button.

Now you have two lists of the same contacts - one for data entry, and one to save.

As an alternative to data entry view, your volunteers can use paths. In single-person view, your volunteers can move a person from one path step to the next to signify that they have completed logging a contact. Using paths to simplify this workflow circumvents the necessity of creating a list for the purpose of of data entry altogether.