I wonder whether I can clear the output of a query in pgAdmin III (aside from running another query).
I found this to be an interesting "lapse", if not bug, in the (normally excellent) pgAdmin3 software.
I double checked and it is is not possible to do what you want on Windows. Update, nor is it possible on Linux. Maybe a feature request? Though, at least the behaviour is consistent: ;-)
With respect to a feature request - it appears that the list is indeed the recommended method of submission. If you provide a link here, I can update with either the Linux or Windows behaviour - whichever you may not have.