How to show or hide primary in UISplitViewController in iOS 14 / macOS 11?

With all the changes to UISplitViewController for iOS 14 and macOS 11 Catalyst, is there now a simple way to show or hide the primary view controller when it's using displayMode == .automatic? Basically a way to programmatically do what the displayModeButton does when it's tapped?

I've tried invoking the new .hide(.primary) method, which does indeed hide the primary as advertised, but unfortunately the display mode button also goes away so the user has no way to get the primary back again.