Form Design mode is the system mode in which it is possible to create and edit master forms, report designs and director groups.
In single user (desktop) Formever systems the system is always in form design mode. Except when it is in admin mode.
In multi-user (cloud) Formever systems Form Design mode means that other users of the system are signed out and only a single user (a director of the correct role) can create and edit master forms, report designs and director groups.