from https://forum.dlang.org/thread/[email protected]:
can't collapse/fold a case statement in the editor for some reason ;/
case statements are blocks. They might not be represented as such but they are semantically the same as blocks. The representation is irrelevant. Since, in D, every case must end with a break or return or throw, it means that the next case terminates the block automatically.
So, all that needs to be done, if it is possible is to collapse everything up to the next case statement or terminal }.