I have solved the issue myself, I configured default values on the main product item and set this default item in the configuration of product syncing application. once we sync products, from our (out of Odoo) E-Commerce platform to smoothly takes it.

If to be done manually, then setting defaults on product category form will help. (enable developer mode to see that). So every new category will follow defaults.

***My case was anglo-Saxon accounting and inventory valuation auto with Stock value, Input and output account.