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