The "Add" button on the Classes page in the Unassigned section allows you to search for and add an Enrollee straight to the Unassigned list.
If you select the checkbox, it will send an enrollment confirmation email upon adding the Enrollee.
Tooltips are on the "Assign," "Re-enroll," and "Add" buttons showing additional information about what that button does.
Assign Enrollee to Class(es)
Re-assign Enrollee to a different Program
Add Enrollee to the Unassigned List