我想我明白你的意思了，下面是更新添加到列表中的值的代码，当然这段代码可以增强以避免样板代码：

@State private var oldLandingName: String = ""
@State private var newLandingName: String = ""
@State private var isAddingLanding = false
@State private var landings: [String] = []
@State private var isEditing = false

var body: some View {
    NavigationView {
        ZStack {
            Color.blue.ignoresSafeArea()
            Circle()
                .scale(1.7)
                .foregroundColor(.yellow.opacity(0.60))
            Circle()
                .scale(1.3)
                .foregroundColor(.blue.opacity(0.50))
            
            VStack {
                HStack {
                    Text("Add Your Travels")
                        .bold()
                    Spacer()
                    Button(action: {
                        isAddingLanding = true
                    }) {
                        Image(systemName: "plus")
                            .resizable()
                            .frame(width: 20, height: 20)
                            .foregroundColor(.white)
                    }
                }
                .padding(.horizontal)
                
                List(landings, id: \.self) { landing in
                    Text(landing).bold()
                        .foregroundColor(.white)
                        .listRowBackground(Color.clear)
                        .listRowSeparatorTint(.blue)
                        .onTapGesture {
                            self.isEditing = true
                            self.oldLandingName = landing
                            self.newLandingName = landing
                        }
                }
                .listStyle(.plain)
            }
            
        }
        .navigationBarTitle(Text("Landings!"))
        
        .fullScreenCover(isPresented: $isAddingLanding, onDismiss: {}) {
            VStack {
                TextField("Where did you go? \(newLandingName)", text: $newLandingName)
                    .textFieldStyle(RoundedBorderTextFieldStyle())
                    .padding()
                Button("Add") {
                    if !newLandingName.isEmpty {
                        landings.append(newLandingName)
                        newLandingName = ""
                    }
                    isAddingLanding = false
                }
                Color.blue.ignoresSafeArea()
            }
        }
        .fullScreenCover(isPresented: $isEditing, onDismiss: {}) {
            VStack {
                TextField("", text: $newLandingName)
                    .textFieldStyle(RoundedBorderTextFieldStyle())
                    .padding()
                Button("Update") {
                    if !newLandingName.isEmpty {
                        if let idx = landings.firstIndex(where: { $0 == $oldLandingName.wrappedValue }) {
                            self.landings[idx] = newLandingName
                        }
                    }
                    isEditing = false
                }
                Color.blue.ignoresSafeArea()
            }
        }
        
    }
}

我希望这对你有帮助，只是试着理解SwiftUI状态的使用，因为我们有@State和@Binding来处理结构体，还有@StateObject和@Published来处理类。不过，还有其他属性 Package 器可以使用。