You can only import custom form styles for invoices and estimates, kq.
We don't have a specific time-frame yet to when this will be added. As a workaround, I'd suggest creating a customize receipt through QuickBooks Online. You can customize not only sales receipt, but also invoices and estimates.
See How to customize invoices, estimates, and sales receipts as your reference.
And of course, you're always welcome to post again in the Community if you have any other questions.
