Hello, I currently have an experiment that is running. I want to re-use the exact group of users from the control group for a new experiment and expose them to a new feature. Is there a way to do that?

There isn't a way to do this very neatly with GrowthBook right now. You'd have to somehow look up for the user that they were in the control group and set that as an attribute in the app. We're exploring saved groups to help solve this issue in the future.