The new feature to add a service at checkout is great, however there should be an option to "add time" with the service because without doing so it is negatively impacting someones utilization which is a key KPI in evaluating providers and their success within a business and its profitability.
Perhaps you can add the option to "add time with this service" as well for those of us who need it without having to leave the screen and add the service in to the appointment the regular way which would ensure that time is added and utilization is optimized. Otherwise, we wouldn’t be able to fill that time slot anyway at checkout as it would be too late.