BMS reset is only needed after replacing the main battery. The support battery has no sensor.
In your case simply do nothing. The battery management still adapts to the new battery, but it takes a little bit longer to be correct. Nothing to worry about. The BMS reset resets the battery timer, which is the only way to precisly tell the age of the battery or at least when it was installed in your car, and also tells the battery management to adapt to a new battery. This should never be performed without actually replacing the main battery.