SwiftUI: do NavigationView attributes needs to be copy-pasted in each View?

You can create a custom ViewModifier that holds all your common toolbar modifiers.

struct MyToolbar: ViewModifier{
    //Use shared router
    @EnvironmentObject var viewRouter: MyViewRouter
    //Add unique title for each instance
    let title: String
    func body(content: Content) -> some View {
        content
            .navigationTitle(title)
            .navigationBarTitleDisplayMode(.large)
            .toolbarBackground(.blue, for: .navigationBar)
            .toolbarBackground(.visible, for: .navigationBar)
            .toolbarColorScheme(.dark, for: .navigationBar)
            .toolbar {
                Button {
                    viewRouter.mostraProfilo.toggle()
                } label: {
                    Label("User Profile", systemImage: "person.crop.circle")
                }
            }
    }
}

You can share common navigation actions with the use of a ViewRouter that is accessible to all.

The portfolio Button is a good example.

///Router to share navigation
class MyViewRouter: ObservableObject{
    //Shared portfolio variable
    @Published var mostraProfilo: Bool = false
    //You can also add things like a `NavigationPath` to make navigation easier.
    
    enum ViewOptions: String, Hashable{
        //Create a case for each view
        case something
        case somethingDifferent
        //Set the title for a view
        var title: String{
            switch self{
            case .something:
                return "Something Title"
            case .somethingDifferent:
                return "different"
            }
        }
        //List the views for each option
        @ViewBuilder var view: some View {
            switch self{
            case .somethingDifferent:
                VStack{
                    Text("something different")
                }
                //Add individually
                .modifier(MyToolbar(title: "different"))
                //View specific modifiers over the common toolbar for overridding 
                .navigationBarTitleDisplayMode(.inline)
                .toolbarBackground(.red, for: .navigationBar)

            case .something:
                VStack{
                    Text("something")
                }
                //Add individually
                .modifier(MyToolbar(title: "something"))
            }
        }
    }
}

Your Views can then use these shared Options and modifiers.

struct SharedNavigationModifiers: View {
    @StateObject var viewRouter: MyViewRouter = .init()
    var body: some View {
        NavigationStack{
            VStack{
                NavigationLink("go somewhere", value: MyViewRouter.ViewOptions.something)
                NavigationLink("different", value: MyViewRouter.ViewOptions.somethingDifferent)
            }
            //Everone can display this portfolio using the Router
                .navigationDestination(isPresented: $viewRouter.mostraProfilo) {
                    Text("Portfolio View")
                    //Add to each View
                    .modifier(MyToolbar(title: "portfolio"))
                }
                .navigationDestination(for: MyViewRouter.ViewOptions.self) { option in
                        option.view
                    //Add to all options for a more standard look or individually (See Options)
                        //.modifier(MyToolbar(title: option.title))
                    
                }
        }
        //Inject router so all `View`s in Stack have access
        .environmentObject(viewRouter)
    }
}