Eclipse's Navigate | Open Resource menu option missing

The Eclipse "Open Resource" dialog is great but I tend to forget the keyboard shortcut (Ctrl-Shift-R), and I rely on the existence of the Open Resource menu option to remind me. However this menu option is often missing from my current project perspective.

These are the steps to add the Open Resource menu option to the current perspective:

1. Window | Customize Perspective...
2. Command Group Availability tab - check "Resource Navigation"
3. Menu Visibility tab - check "Open Resource..." if it's not already checked
4. OK