An Assignment Flow element is a logic element that allows you to set values in variables, collection variables, record variables, record collection variables, and global variables1. You can use an Assignment Flow element to assign the support representative name to the custom field on the Case object based on the case origin. This way, you can automate the case assignment process without writing any code or using any formula. A trigger, a formula field, and a validation rule are not the best solutions for this scenario, as they either require code, are not dynamic, or do not change the field value. References: 1: Flow Element: Assignment - Salesforce