In the Banking page of QuickBooks Online (QBO), the payee is already unavailable under the Categorized tab.
Please be advised, this info isn't lost. The system has it saved in a different location. You can view it in the register of the bank account in question. You can click the Go to bank register link.
Here, you'll find the Payee Account column. It's divided into two, where the payee is on top, while the account you assigned to the transaction is at the bottom. You can refer to the sample screenshot below which shows a couple of examples.