When going to Page Designer and viewing the page options for a page that contains a List Builder list, there is a field for Required columns in the List Builder section.
The Required columns field will not set defaults for the columns that appear in the List Builder list or in the list of available columns to choose from in the Columns drop down, rather this setting is for developers who are adding actions and forms to the ListBuilder. The Required column setting marks the system IDs for the selected fields as required which stores them for use with other forms that require this data as necessary for later use. This is not a way to default or require fields in the ListBuilder itself for the end user.
In order for the user to control what columns to display in the ListBuilder list, see the following knowledge base solution:
1. Go to a page that contains a List Builder list, for example, Direct Marketing efforts located in Marketing and Communications\Marketing Efforts\Direct Marketing Efforts 2. Enter into Page Designer by clicking the toggle design mode icon in the top right of the page 3. Directly above the List Builder list click Properties to open the Edit page section window 4. In the Edit page section window scroll down to the List builder section 5. Note the field called Required columns: