It would be helpful for the Header calculation to include more than a single ply member as most headers are 2+ plies.
Guest
Headers in Standard orientation can be designed as multiple plies. You can change between Standard and Plank orientation on the Product Selection tab.
Forte already does multiple ply members, maybe you should contact support and have them explain how to use the program better? The only limitation of single ply members is headers in tall walls with lateral loads and in situations where you specified plank orientation.