Thanks for becoming a part of the Community, vanny_uk.
 

The most recent feature request about sorting customers by last name was submitted to our product development team on January 20, 2020. I'll resubmit a new inquiry about it and adding multiple contacts today for you. These are sent as requests, so there's no guarantee the abilities will be created. Currently, the workaround recommended by my colleague, FritzF, is how to sort customers this way in QuickBooks Online.
 

I recommend keeping an eye on our What's New in QBO Archives. In there, Intuit publishes details about recent and upcoming changes to the product which help keeps subscribers up-to-date on what's going on.
 

If there's anything else I can assist with, feel welcome to reach out anytime. Enjoy the rest of your day!