Another feature from IntelliJ editor that is too nice to do without:

On the left hand side of the editor bar, there should be a downward arrow for
all interface/superclass/overridden-method delarations that have
implementing/subclass/overriding code.

. If it is an interface/superclass, onclick of the downward arrow, a dropdown
list should show all the implementing/subclass; and, onclick of the
implementing/subclass name, the class show open in editor.

. If it is an overridden method inside the interface/superclass, onclick of the
downward arrow, the dropdown list should show all the overriding methods in all
implementing/subclasses; and oncick of the overriding method name, the editor
should open and navigate to the selected overriding method.

Vice versa, an upward arrow should exist for all
implementing/subclasses/overriding methods; the user should be able to use it to
navigate to the super code.