Welcome to the Community, @info-southernlux.
I understand that having this feature is a great help. However, this is only available in our Desktop version of QuickBooks. You may want to visit our Intuit blog for the latest product updates.
You can also set up or change customer messages in QuickBooks Online. This helps you print messages on the statement or change the greetings on the sales forms.
Feel free to ask if you have additional questions. We are here to help. Have a great day.