Under the Recipients tab of a sent email blast, you can add people from different categories (sent, unopened, clicked, etc.) to a list by clicking on the + above the column of names in that category. It appears that this functionality times out if the list size exceeds 60k. The error reads, "There was an error adding these people to your list. Please try again." It is still possible to isolate recipients from the sent, opened, and unopened categories through the People tab using a filter.
This problem has been addressed - adding to list from a particular email stats view now functions as expected as of December 6, 2018.