I can see the benefit of importing the desired quantity to be added or reduced in the inventory, dchen16.  However, this feature isn't yet available in QuickBooks Online (QBO). With this, I'll encourage you to send feedback or product recommendations to help improve your experience using the platform.

You can follow the steps provided by my colleague above on how to submit feedback. You can also track feature requests through the Customer Feedback for QuickBooks Online website.

Additionally, we've assembled several frequently asked questions about importing data to QBO to clarify things for you: Common questions about importing data to QuickBooks Online.

Keep in touch whenever you need additional assistance in making bulk adjustments within your account. The Community is available anytime to help you. Be safe and have a great rest of the day!