Here is the most recently updated guide for archiving past performances.
In short, (and covered in a different forum post) ‘Hiding’ replaces ‘Archiving’ and ‘Archiving’ now means ‘Moving a folder to an archive folder’.
A large part of it is a change in terminology. Keep hiding folders as regularly as you were archiving them (to get them out of the folder tree view in admin), but once you have finished with them (i.e. made all sales and done all the reporting you need to do), then its time to carry out the new ‘Archive Hidden Folders’ functionality.