Hi Rahul,
You can assign additional tariff scheme to the numbering scheme of tariff code numbers as coding scheme. You need to also upload the additional chapters in the system either manually or with upload xml option. The system then adds these additional chapters in the classification help which you can call to assign them at item level during customs declaration processing. Whether or not you need additional tariff code for the item depends upon the tariff code which is assigned to product. If the additional tariff code is required for the product tariff code, system displays the function to assign these additional tariff codes at item level during document processing.
I am not sure if the requirement for additional tariff code is mandatory or optional but you can try with this additional coding scheme configuration step share the outcome on this thread.
Thanks - Pushpraj