Edit Product Rate 

Click on 'Products' tab from drawer menu (below transactions tab)

You will be able to view products list

Click on Rate button (in purple border) 

You will be Redirected to product rate screen

Click date in calendar then add / edit rate modal opens 

For GST enabled products, shows rate without GST, HSN code of product, GST % applicable

Enter rate in modal input 

Click on 'Done' button