I\'m finally starting to get over my initial frustrations with Xcode 4.0 (why on earth did they think changing all of the keyboard shortcuts was a good idea).
Howeve
Xcode 8.3.3 - German Keyboard
Cmd + Shift + <
Update:
In fact there is a keybinding in Xcode that overides the system wide shortcut to switch between windows on german keyboards. The keybinding is Cmd + < for Scheme > Edit Scheme.
When this shortcut is changed or removed, then the usual shortcuts to cycle through the open windows of an application will work as expected (i.e. Cmd + < cycle forward, Cmd + Shift + < cycle backward).