Never mind my reply above which I have now edited.
The question is too vague because there are two different things at play. First is the port forwarding part which UPnP does handle but of course the same destination port on the external address is only usable for one port forward, no way around it on pfSense or any other platform. The next thing is the outbound NAT configuration and this is what I think the question is really about and this is something the UPnP service in pfSense doesn't automate as far as I know.