Adding firewall output rule for the router through Luci

Hi everybody,

Here is a question about adding firewall rules using the Luci Web Interface:

I created a new firewall zone for which the default output policy is DROP. I would like to use the Luci web interface to add a new firewall rule that ACCEPTs the output traffic from the router itself to this zone. However, for the Source Zone parameter, there is no entry like Device(output). Any zone or one of the existing zones must be selected.

So how can I do that?

Is it possible to make the router appears among the choices available for Source Zone? Or is it possible to create a new firewall zone that represents the router itself and make it available in the list of zones for Source Zone?

(Note that Device(input) is available for the Destination parameter. So why not Device(output) for Source Zone?)

Thank you in advance for your precious help.