Hello,
I was talking about a possible evolution in the future.
Something which is not possible for the moment since I wrote :
You can have only one product template for a vendor.
Which is the current state of the product templates.
I mentioned a trigger yes but I also added :
There is a trigger to interact with the product template but that trigger is only when a new product is submitted. So in your case it won't feet to your needs.
If you just want to change the default product quantity, the best is to use a view override of the "productmarket / form" view.
Thanks to
if(empty($this->product->product_id)) { }
You can know that you're editing a new product and you can change the value of the product_quantity depending your own condition and algorithm.
Regards,