Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Filename
SUBSTANCEASSET_FILENAMEParameter: Auto Update
SUBSTANCEASSET_ENABLEDParameter: SUBSTANCEASSET_GROUP_STATUS
SUBSTANCEASSET_GROUP_STATUSParameter: Disable Legacy
SUBSTANCEASSET_NO_LEGACY_GAMMA