If you wish to better organize your products (add / edit / remove) and also arrange them under Categories, for a better product management, please use the Inventory section, at the top:

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Here, you will find 3 main sub-sections, pretty self explanatory:

1. Products  – where all your products are listed (for more info on how to add a product, please click here)

2. Add Category – allows you to add new categories of products to your inventory

3. Categories – lists all the categories

If you wish to change the category where a product is listed, you will simply need to click on the product, scroll down to Categories and choose a different one from the drop-down.