Assignees are automatically sorted alphabetically, but it would really help if I could either drag people around (so I can see a group of people’s availability side-by-side) or in some other way customize the order they show up in.
Thanks for sharing your feedback with us, @Bethany2! We don’t have immediate plans to implement this option, but I’ll let you know if you have any news in the future 
If you are managing your team’s capacity and availability, I also recommend you to check our Workload feature: View Your Team's Workload in Asana | Product Guide • Asana Product Guide