other protocol support

CPF 2.3, attempting to add a new rule to ALLOW GRE, the protocol drop-down does not contain
that (as well as several other) protocols.

how do I add such a rule?

(btw: all initial rules were deleted by a cockpit error on my part (:SAD) )

If you select IP as the protocol & then go to the IP details tab, you’ll see GRE (and others) there. It changes depending on what protocol you select.