Be careful. Sorting sources in alphabetical order doesn't make sense, because the order is important. It's a stack of sources. A source above another source is really above that other source and obscures what's under it.
About sorting scenes: if you have that many scenes that you need sorting, you should think about your scene design. It's not practical to have an immense amount of scenes. May be grid mode and intelligent manual sorting result in better overview instead of sorting: right-click within the scene window and choose "Grid Mode" at the bottom.