AWS D1.1 Structural Welding Code/Steel only includes F-number 1 through 4.
If you dig through D1.6 Structural Welding Code/Stainless Steel, there is a provision (4.7.5) that states "with the approval the Engineer" a welder qualified using any Group I or II steel listed in D1.1 is also qualified to weld any steel listed in D1.6. That assumes the welding procedure is either qualified by testing or is a prequalified WPS and is for the same welding process.
However, the same provision is not in AWS D1.1, so a welder qualified with a base metal listed in D1.6 is not qualified for D1.1. That being said, the Engineer always has the last word in such matters.
Best regards - Al