In the categories page you can easily group related products together by creating a category by clicking on the "+" button and giving it a name.
Then, on that category page you can drag which products you'd like to include in that category by clicking on the "+" button and selecting the products you'd like to include.
A category allows you to easily apply discounts in bulk to all of the products in that category.
You can also assign a different Discord channel webhook just for the category, so sales of that product could appear in a different room, even in a different server. That might be useful, for example, when creating products in collaboration with other people.