It's good to see you here in the Community, @ramya3.
Allow me to provide some information about printing an invoice with GSTIN and importing a credit note.
You'll want to make sure that the exported invoice has a tax code so the GSTIN will show when printing it. To verify, let's find and open the invoice. Here's how:
On the other hand, the option to import credit notes in QBO is currently unavailable. You can consider entering them manually into your QBO account. For more guidance, feel free to check out this article: Create and apply credit notes or delayed credits in QuickBooks Online.
You might also want to design your own invoice or estimate templates and import them into your QBO account. Here's an article you can read for the detailed steps and information: Import custom form styles for invoices or estimates.
Our doors are always open to help you again if you have any other concerns about printing and importing transactions in QBO. Have a good one.