Explanation
Use all-or-none scheduling for related appointments is a setting in Field Service Settings that enables or disables the simultaneous scheduling of service appointments that have dependencies[232]. Dependency Type is a field on the Service Appointment object that defines the relationship between two service appointments such as Start After Finish, Start Before Finish, or Finish Before Start[233]. Same Resource and Same Day are fields on the Service Appointment object that indicate whether two service appointments with dependencies should be assigned to the same resource and scheduled on the same day[234]. Selecting the checkbox Use all-or-none scheduling for related appointments in Field Service Settings, setting the Dependency Type to Start After Finish and Same Day on the first service appointment in the dependency, and making sure the Same Resource and Same Day fields appear on the Service Appointments page layout would allow Universal Containers to ensure that a customer makes one appointment for the sales department, and another appointment for the service department, that should be handled on the same day, but should be created as separate appointments, where the Technician must complete one appointment before starting the next, and that these two appointments are scheduled together and in sequence by enabling simultaneous scheduling of dependent service appointments, defining the order and timing of the service appointments, and ensuring that the service appointments are assigned to the same resource and scheduled on the same day[235]. Creating a dependency between the two appointments and setting the start times to be the same would not work because it would not ensure that one appointment is completed before starting the next. Adding the Complex Work Visualforce page to the Service Appointments page would not work because it is not a feature of Salesforce Field Service. References: https://help.salesforce.com/s/articleView?id=sf.fs_settings_overview.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.fs_service_appointment_dependencies_overview.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.fs_service_appointment_dependencies_create_edit_delete.htm&t