I don't think there is a shortcut for viewing Indirect Fire Spotters.
I seem to have to use this from the menu a lot when moving artillery around and in some games you have to move the guns many times.
I always appear to be forever diving into the menu to highlight these spotters and then having to come out to highlight organisation for other units I'm moving.
I think it would be really nice if possible to incorporate a keyboard shortcut for this or a button even if it's at the expense of some other far less used button or shortcut.
Perhaps others feel similar or have some comment on the subject.
Cheers Gordon