How to display parent(s) methods/variables in Outline?

For completeness: pressing Ctrl-O in an editor opens the outline view as a popup. Pressing Ctrl-O again adds all inherited methods to the popup.

Not in the Outline View but in the Type Hierarchy View:

With the cursor in your class name, click F4 (or select "Open Type Hierarchy" in the context menu). You'll see the Type Hierarchy View, where you can click "Show all inherited members".