Ignore this reply - tables preview fine but dont post fine

So if I am understanding this correctly it would go: NavigationSplitView { View { ...Sidebar } TabView { NavigationStack { List { .... } .toolbar { Primary / Secondary Action } } } } .onChange(of: sizeClass) { manage detail / automatic }

@Environment(.horizontalSizeClass) private var hSizeClass sorry again that didn't keep After I posted again

You can check if the size class is .compact so it is one screen or .regular where it is both using You can use that to determine controls while in compact mode

Sorry can't edit for some reason it removed getting that variable @Environment(\.horizontalSizeClass) private var hSizeClass

If hSizeClass == .regular { // Unfolded } else { // folded }

You could use a an ArrangementView and have your app content in primary and for secondary a view that directs people to put another app there. I am unsure if this would be accepted per the app guidelines however