There are a few design possibilities. Adding an "All" in the area drop down would be one option. Converting the dialog to use a tabbed notebook might make it more obvious. Having the search function scan all possible matches if the current drop down Area does not contain the search key and pop up a table of choices would be another possibility.
I imagine the command is not listed in the available keyboard shortcuts documentation because the function is not bound to a shortcut. As you can see be reviewing the Keyboard Shortcut dialog, there are quite a few functions that do not have active bindings. Listing them all in the table along with the current active bindings would make the list of active bindings difficult to read. Maybe adding a table of functions as an appendix to the documentation would be useful.
In any event, glad you got it working.