Is there a way to Delete all groups at once? I would love to be able to do this. There doesn't seem to be a way that I can find.
Not currently, no. If you would like that feature please make a feature request.
http://answers.presonus.com/studio-one-feature-requests
Please read through the previous posts to see if your request is already added by another user. If so, post in their listing to add to the numbers requesting the feature you would like to see added.
Link to previous feature requests:
http://answers.presonus.com/questions/studio-one-feature-requests?sort=views