This is a new feature in version 6.20.
A constant and unavoidable frustration occurs when you find that you need to work on a parent class for the form or class you are editing (or one of its members). What you need to do, of course, is to close the form or class you are working on and then find and open the parent class. This new feature simplifies the task of finding and opening the parent class, so that it can be done entirely within PEM Editor.
These are the few steps to be followed:
(1) Make sure that PEM Editor is displaying the form/class/object whose Parent Class you want to open.
(2) Open the context menu from the combobox, and select 'Save Parent Classes'.
(3) Close the current form or class.
(4) Click on the 'Open' icon at the top of PEM Editor. Under the menu item 'MRU Parent Classes' will be listed all the parent classes (all of them ... all the way back), and you can select which Parent Class you need to modify.