Designer babies are considered socially unacceptable in many parts of the world.

Hm. Maybe we are really socially isolated then, but as a couple we were never really interested in what will other people think if we do something (we both are the not having many friends type), and we would have jumped on the option of having an easy baby, no learning difficulties, not crying during the night, and of course perfectly healthy. Granted, we would not edit things like hair or eye color because it would feel like an unwelcome intrusion into other person's individuality even when the person does not exist yet. But we would edit out the potential problems.

I remember how we were full of fears of getting a Downs case or worse. Plain simply we were not 100% sure of our ability to give a fully healthy child the time investment she needs, we would not have been able to deal with a disabled one who needs much more. Thankfully we have a healthy baby although developing smaller than usual, but the fear was there and we would have gladly accepted the option to not have this fear. I don't understand why would be a social stigma against e.g. fixing Downs. Of course things like customizing hair color is a bit too frivolous to me too, but that is a different story. I would also not give things like a musical talent because we cannot know if it does not lead to problems down the road like having a calling to something else, yet choosing to work in the talent as that is a safer career.