This option opens the appropriate attribute editor dialog - depending on the type (also called 'LDAP syntax') of the currently selected attributes. Two examples:
The editor for integer attributes:
The editor for distinguished name attributes:
If there were more than one attribute selected in the list, you see a special dialog for editing multiple objects - this allows you to change values for several objects with one single edit operation:
To edit the value of an object, you can also select it in the list and press ENTER. There may be situations where the Edit Value option may be disabled. This might be if the LEX ReadOnly Mode is active, or when the application focus doesn't lay on the attribute list.