I’m creating an app in Swift for MacOS and I’m adding a settings view.

Here where is defined:

struct MyApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        Settings {
            SettingsView()
        }
    }
}

Here is the SettingsView:

struct SettingsView: View {
    
    var body: some View {
        TabView {
            GeneralSettingsView()
                .tabItem {
                    Label("General", systemImage: "gear")
                }
        }
        .scenePadding()
        .frame(maxWidth: 350, minHeight: 100)
    }
}

GeneralSettingsView:

struct GeneralSettingsView: View {
    enum FolderSelection: Hashable {
        case predefined(URL)
        case other
        
        var url: URL? {
            switch self {
            case .predefined(let url):
                return url
            case .other:
                return nil
            }
        }
    }
    
    @AppStorage("destinationFolder") private var destinationFolder: URL = {
        if let downloadsDirectory = FileManager.default.urls(for: .downloadsDirectory, in: .userDomainMask).first {
            return downloadsDirectory
        }
        return URL(fileURLWithPath: "")
    }()
    
    @State private var destinationFolders: [(name: String, url: URL)] = [
        ("Downloads", FileManager.default.urls(for: .downloadsDirectory, in: .userDomainMask).first!)
    ]
    
    @State private var selectedFolder: FolderSelection = .predefined(FileManager.default.urls(for: .downloadsDirectory, in: .userDomainMask).first!)

    var body: some View {
        VStack {
            HStack {
                Picker("Destination folder:", selection: $selectedFolder) {
                    ForEach(destinationFolders, id: .url) { folder in
                        Text(folder.name).tag(FolderSelection.predefined(folder.url))
                    }
                    Text("Other...").tag(FolderSelection.other)
                }
                .onChange(of: selectedFolder) { newSelection in
                    handleFolderSelection(newSelection)
                }
            }
        }
        .padding()
    }
    
    private func handleFolderSelection(_ newSelection: FolderSelection) {
        switch newSelection {
        case .predefined(let url):
            destinationFolder = url
        case .other:
            selectFolder()
        }
    }
    
    private func selectFolder() {
        let panel = NSOpenPanel()
        panel.canChooseFiles = false
        panel.canChooseDirectories = true
        panel.allowsMultipleSelection = false
        panel.prompt = "Select folder"
        
        if panel.runModal() == .OK, let selectedURL = panel.url {
            let newFolderSelection = FolderSelection.predefined(selectedURL)
            
            if !destinationFolders.contains(where: { $0.url == selectedURL }) {
                destinationFolders.append((selectedURL.lastPathComponent, selectedURL))
            }
            
            selectedFolder = newFolderSelection

            destinationFolder = selectedURL
        } else {
            selectedFolder = .predefined(destinationFolder)
        }
    }
}

The problem happens when, once the new folder is chosen, the settings view disappears, instead of remaining (like when you choose the Downloads folder in the Safari settings).
What is the problem?