About time. This is the other thing that GCP does so well and I was puzzled that AWS still couldnt do - just add more than one keys to a EC2 instance through the API (https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-inst...).
There are tons of support questions about "how can I add multiple SSH keys to my EC2 instances".
Now if only AWS brings in "projects". That's the last usability edge that GCP has.