Thank you very much for those links. After a couple of hours of messing around I have managed to get that working well. :)

I want the ability to use Google/G-Suite as an identity provider to log into multiple AWS accounts. We have dev and prod workloads that run in completely separate AWS accounts. I want to be able to use Google SSO and the ability to select which AWS account to log into

I don't have access to a G-Suite account to test this with, but afaict you should be able to do this by just adding each AWS account in turn and giving it a different Application Name and description in the G-Suite interface.