When we create Alternate key with 2 fields (1 field is NOT NULL and second is NULL) - TOAD Data Modeler automatically sets field that was nullable to NOT NULL and grays it. We can’t update that field to reqiured state - it must be optional (NULL).
So TOAD sets ALL fields in Alternate Key as NOT NULL.
TOAD Data Modeler 22.214.171.124
DB: MS SQL 2005