I'm just curious why the Leonardo Express (https://en.wikipedia.org/wiki/Leonardo_Express) isn't included in the Ferrovie Laziali (itafl) system.
Because it's not part of that system.
It will be there next update as a route, as is Travel Mapping's first (and finale) foray into the smallest country in the world - the weekly tourist train between Papal palaces run by the Vatican Museum.