I understand you'd like to permanently set the Standard template as the default for your imported invoices.
Currently, QuickBooks Online is transitioning all users globally to a new invoicing engine, and the Batch Import tool has been updated to use the Modernized Template as its primary framework.
In the meantime, you will need to manually change the template for each invoice after importing.
To do this, open the invoice > View/Edit > Manage > Design > select Standard.
If something’s still unclear or you’ve got more questions, feel free to drop a comment below. We're happy to help and make sure everything’s running smoothly for you. Have a great day!