Hey there learn-itchysalph,
Welcome to the QuickBooks Community! It's always a pleasure to see new faces. QuickBooks Online is a great tool that has various features to help make running your business smoother. I would be happy to provide some information.
At this time, the option to add inventory to QuickBooks Online essentials, isn't available. If this is a feature you feel you may benefit from, I recommend upgrading your subscription to either QuickBooks Online Plus, or Advanced. If you decide you'd like to upgrade your subscription, This helpful guide will provide the steps on how to add inventory to QuickBooks Online Plus and Advanced. I hope this helps!
If you have any other questions, Feel free to reach back out to us here.