This property type is used to choose several items from a list of valid values supplied as the right argument to the type name in the class specification. For example:

Garnish : ManyOf 'Lettuce' 'Onion' 'Peppers'  © Salads

... or you may hold the list as a variable in the class namespace ...

Garnish : ManyOf ‘salad © Salads

The expression giving the option list is executed by the Designer whenever you switch focus to an object of that type, causing the property-watcher to rebuild itself. It may be a simple list (vector of text vectors) or a two-column matrix giving short codes and a longer description. In this case the Designer will show the longer description in the popup-selection but store the short code in the dialogue box.