this was requested way back and goes along with a sort of function library for use in FF, that library being comprised of imported snippets and other filters. it also goes hand in hand with that thing of compressing large routines down into a single component and being able to call that component up from the filter.
i like uber's method, too. having access to other filters from within another filter is a great idea.
i could also see having more than one editor open at a time for quick copy/paste operations. tabbed editor windows

If wishes were horses... there'd be a whole lot of horse crap to clean up!
Craig