Opencart duplicate module example
From Wiki at Neela Nurseries
2018-07-01 Sunday: how to duplicate handling fee module in Opencart
Overview
Want to add a fee similar to Opencart's default handling fee for ship-able orders. Free but technical way to do this is to duplicate files which implement the handling fee, making changes in them so they appear as a new Opencart module in Opencart's Extensions -> Order Totals admin page.
Locating Existing OC Module Files
Searching for handling fee related files in Opencart 2.3.0.2 root directory:
$ find . -name '*hand*' ./admin/view/template/extension/total/handling.tpl ./admin/language/en-gb/extension/total/handling.php ./admin/controller/extension/total/handling.php ./catalog/model/extension/total/handling.php ./catalog/language/en-gb/extension/total/handling.php $