Code folding doesn't work with key binding Shift + Alt + Cmd + <- left in Xcode 9. Is anyone having same problem with Xcode 9?
Code folding is one a long list of things that isn't implemented in the new editor yet.
UPD:
Now after release of Xcode 9 code folding works now with former shortcut ( Shift + Alt + Cmd + left arrow)
Note: For only folding the scope you are in, press Alt + Cmd + left arrow.