Modifying topic classes and instances

Class is a topic that describes the type of the topic. Each topic may contain zero or more classes.

Class is added to a topic by right-clicking the title header Classes and selecting Add class. Operation employs pick-a-topic-type window used to point the topic class. Topic's class is deleted selecting a row in the class table, right-clicking the row and selecting Loose classes.... Multiple classes can be removed at once.

Also Topics > Add to topic > Add class menu selection adds topic a class and Topics > Delete from topic > Loose classes deletes the class but leaves the class topic intact.