How will I add those details?
I did not fully understand your question. There is an option of selecting if a item or service is Non-GST.
The application I usually use has an option for GST 0. Even Saudi has an option for KSA VAT 0 in ERPNext. I need that option to integrate ERPNext with the application I use
In that case you can create your own zero rate sales/purchase/item tax and charges template.
I just decided to use the exempt option but thanks
That is the best way to do it.