Manually creating/copying "Indoor treadmill walking" activity

Hi!

My Fenix 7 doesn't have an indoor treadmill walking activity. I made one myself by copying the "walking" activity and disabling GPS but it's still not quite the same. Certain bits in the resulting .FIT-file are still different, mainly the "sub_sport" part from "sport"-section. My girls Venu2s does have an indoor walking activity; they've just skipped this on the Fenix-series it seems

Long story short; can I change my manually created indoorwalk (which is a copy of the walking activity) to have a different sub_sport bit ?

Thanks!