The replies above are not answering what OP is actually asking. He wants to automate the App Groups creation process by using the App Store Connect API, not do it manually. I also face the same issue. I don't think it's possible to do this with the App Store Connect API, despite it being released for years now. It's missing other key features as well.
Apple doesn't seem to care about their API very much.
pedrotfig
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution
Last seen
User for