New API Gateway UI doesn't work with existing projects, how to proceed?

Hello, I'm not sure where else to post my concerns.

I've been working on a large project for months on my own and to save time I use the Gateway API UI. The new UI that is being forced on the 30th doesn't support working from a previous project. I know AWS is a busy place, so I'm not counting on it being fixed before launch.

Problems with UI detailed here: https://repost.aws/en/questions/QUn2iCus6hQ6e5vsoQFvn4mQ/cors-errors-specifically-when-using-the-new-api-gateway-ui

What is the best method to move forward with my existing project in the new UI? Do I need to rebuild/remake the entire thing?