Hello there, ld-kore.

Setting up non-recurring invoices is unavailable in Quickbooks Online. As a workaround, you can create a dummy customer profile, and then create an invoice.

More info on creating a recurring invoice is in this article: How to create a recurring invoice and manage recurring transactions. It also includes steps on how you can manage your recurring transactions.

Please feel free to read these handy articles for your reference about managing your invoices: Create invoices in QuickBooks Online.

If you have any follow-up questions, please let me know by adding a comment below. I'm more than happy to help. Keep safe!