I don't follow....can you provide some more information [and/or a picture] for what you need to do here?
Design Manager Streetscape Ltd
Solid Edge ST10 [MP8] Classic [x2 seats]
Windows 10 - Quadro P2000
Here's one way to do it. I took your model, deleted the top flange, and extended the front wraparound flange up. I then drew a sketch at the angle I wanted the top flap to be at eventually, and made a normal cutout across the entire wrapped front flange. I added the top flange and set its extent to the edge of the front flange, and then simply added a corner radius. Below are the steps in pictures, and attached is the edited model.
What has been shown by Chally72 is a perfect solution! Good job!
I think "the life" will be easier in ST7 with the new Part to SM command!