Inserting a module in descriptions can be done in several ways but it can pose some problems based on how you configure everything. So it's not possible to give a one size fit all solution.
For example, if you want to display add to cart buttons in your related products listing module, you will have to move the description display out of the form of the product page or the HTML elements will conflict and the add to cart buttons won't work properly.
The simplest solution though will be to use the joomla extension modules anywhere to insert a display tag for your related products module where you want in the description of each one your products.
HIKASHOP ESSENTIAL 49,95€The basic version. With the main features for a little shop.
HIKAMARKETAdd-on Create a multivendor platform. Enable many vendors on your website.
HIKASERIALAdd-on Sale e-tickets, vouchers, gift certificates, serial numbers and more!
MARKETPLACEPlugins, modules and other kinds of integrations for HikaShop
HIKAAUCTION 40€Add-on Create auctions and let your customers bid for products.
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