Create custom field in admin product-section

I am trying to build an addon for creating a custom field in admin product page, for showing “custom shipping text” for a particular product, as client wishes.

“Shipping Properties” doesn't allow any text to be entered, only values.

I've checked the addon creation document at “” but still confused, as to where to put my custom addon template file for adding the field in admin product section ?

Also how to set field to be bulk value addable & editable in admin ?

Can somebody help me with this ?

My cs-cart version is 4.0.1 multivendor, I guess addon documentation for v4 is still not available in advanced section.

Thanks in advance