Missing .XIB Objects: Migrating existing code to the new look of macOS Big Sur

I have several Objective-C based Mac applications that need to updated to match the new sidebar/full-window-content look of Big Sur. Unfortunately, when I bring up the object library in the .XIB files in my project, I cannot find the objects mentioned in the WWDC video ("Adopt the new look of macOS").

Are objects like NSSplitViewController, NSSplitViewItem and the NSWindowController with a Split View going to be made available in the final release? If not, is there a way for me to adopt the new look without moving my .XIB files to Storyboards?

Regards,


Missing .XIB Objects: Migrating existing code to the new look of macOS Big Sur
 
 
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