3.6 Property Tool
When a property type is of data type string and uses one of
the list widgets, it has a Value list, specifying the values that will
appear in the list widget’s list. The Value list contains a pop-up
menu with the following items:

Add...
prompts for a value and adds it to the list.
Move... allows you to give a new position to the
property value in the list.
Delete removes the selected value from the
list.