I have found that this seems to primarily be occurring when switching from the Debug navigator to the Project navigator. If I switch to any of the other navigators (e.g. Issue navigator) and then go back to the Project navigator, then my previous file hierarchy expand/collapse state is recovered.
prv5850
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution