Find category.js at assets > js > theme
Paste the code below inside the onReady() function
let descBottom = $('.opt7-category-desc-bottom');
if (descBottom.length > 0) {
descBottom.insertAfter('div[data-content-region=below_category_products]');
}
Go to the category description you want to edit.
Select "Edit HTML Source" from the options.
Place your content inside the div like so
<div class="opt7-category-desc-bottom">
//place content here
</div>
An older project that already has this functionality may not be using the opt7-category-desc-bottom selector.
The selector you insert the bottom div can be changed accordingly.