Glad to have you here in the Community, @Mapoissa.
You've got me here to provide clarifications on why you don't have the Inventory option when adding an item in QuickBooks Online.
At this time, being able to track inventory is only available to the Plus and Advanced versions of QuickBooks. That said, if you're currently using the Simple Start or Essentials this option isn't visible.
To get your work done, you may record the inventory in QBO manually. Here's a link that provides completed details on how to perform this process: Track inventory manually in QuickBooks Online.
However, if you wish to track them automatically, you may upgrade the program to the version that supports this functionality.
To do that:
- Click on the Gear icon at the top.
- Press on Account and Settings.
- Select the Billing & Subscription menu.
- In the QuickBooks Online section, hit on Upgrade.
- Choose the plan you want, and tap on Upgrade.
- Confirm your payment information and select Save.
After that, you can now start tracking your inventories in the system. You can utilize these articles I've added to guide you in the set up and in recording them:
Let me know if you have any other questions on this. I'll make sure you're taken care of. Keep safe!