This can be done but there are a lot of variables involved. (If it was a simple mod, I’d package it up as a simple mod!) So I offer it as a service. It’s called Free Shipping Recalculation. It recomputes your free shipping threshold based on the subtotal after discounts.
Free Shipping Recalculation works, whether you are using Admin->Modules->Shipping->Free Shipping Options or Admin->Modules->Order Totals>Shipping to set your free shipping threshold.
This video demonstrates the creation of product packages (groups of individual products) that can be sold as a discounted group with a single click in Zen
Cart, using my mods Discount Chooser and Extended Family.
For a lot of stores, it makes sense to build “product bundles” that can be sold with a single click. As long as your products don’t have attributes, you can easily do this with Zen Cart Extended Family.
Better Together Admin allows you to easily create “buy one, get one” discounts for your OpenCart based store. And it works right through your regular admin panel; no need to edit code to create the discounts. Here’s a video:
I have released Discount Chooser for OpenCart (a port of the Discount Chooser / Free Gift Chooser algorithm from Zen Cart). I’m excited about this software and hope it really helps OpenCart store operators.
Discount Chooser goes beyond the standard BOGO discounts to permit the creation of much broader offers. For example, you can create “Buy 2, get 1”, “Buy 3 get 1,” or “Buy some number, get a choice of some number.”
If you open the stacked three dots menu in your browser (to the right of the address bar) and open “More Tools -> Developer Tools”, then press the stacked three dot menu on that dialog, you’ll see a checkbox under Network with the label “Disable cache (while DevTools is open)”. Check this, and you’ll always be using the freshest copies of your css and js files.