The ability to Customize the List Member View of a marketing list has not been made available in the Customization area of the UI, but can still be achieved with the UI in other means by using the Advanced Find feature.
Jim Schumacher wrote a nice article on how to customize the Marketing List Member views e.g. to add the email address. For exact details on how to accomplish this see his post on Customize Marketing List (List Member View) CRM Team Blog.
Note:
You can also change the Active and Inactive Members views for accounts, contacts and leads by simply changing the Adv. Find to search for Name contains “Member”. See example below:
