List Import Mode is only available for users with a role that has the Advanced List Import permission enabled. All other users won’t see the List Import Mode drop-down when importing a list of people and any list they import defaults to the Normal import mode.
Admin Permissions Required
Go to Admin.
Click Users & Roles.
Under the Roles tab, select the role you want to modify and click Edit Role.
Under Access Database, check Advanced List Import then click Save.
Cool! Now all users associated to the role you edited will have advanced list import options enabled.