Thanks for joining the thread, @blossombird.
We want to ensure everything is working well for you. In the meantime, we highly suggest that you talk with the Square Team to have them check what's going on with the modifiers. This community can only help with QuickBooks related concerns.
As a workaround, you may follow Fiat Lux - ASIA's suggestion to use a connector app. We have an app store where you can check for tools that will help you. Click this link to our website: https://quickbooks.intuit.com/app/apps/home/
If you have other QuickBooks concerns, please feel free to mention my name or post here again. I'll be right here to assist you anytime.
