For Groups you need to go to the the new "Devices" page and up in the top right corner is "See More". That will take you to the old-style "Groups" page where you can add groups etc.
"Scenes" on the other hand have gone missing. I'm finding that if I add scenes to a room or zone in the Philips Hue App, they will eventually show up in Alexa. I have not tried removing a scene. The only way you can get at Scenes in Alexa, at the moment, is to add one as a line item in a routine.
To get them to bring back the "Scenes" page everyone needs to go to the "Help & Feedback" page in the Alexa App and use the "email" option, as they don't pay any attention to these or other forums.
Kyle