How can I avoid nested Navigation Bars in SwiftUI?

You should only have one NavigationView in your view hierarchy, as an ancestor of the menu view. You can then use NavigationLinks at any level of the hierarchy under that.

So, for example, your root view could be defined like this:

struct RootView: View {
    var body: some View {
        NavigationView {
            MenuView()
                .navigationBarItems(trailing: profileButton)
        }
    }

    private var profileButton: some View {
        Button(action: { }) {
            Image(systemName: "person.crop.circle")
        }
    }
}

Then your menu view has NavigationLinks to the appropriate views:

struct MenuView: View {
    var body: some View {
        List {
            link(icon: "calendar", label: "Appointments", destination: AppointmentListView())
            link(icon: "list.bullet", label: "Work Order List", destination: WorkOrderListView())
            link(icon: "rectangle.stack.person.crop", label: "Contacts", destination: ContactListView())
            link(icon: "calendar", label: "My Calendar", destination: MyCalendarView())
        }.navigationBarTitle(Text("Menu"), displayMode: .large)
    }

    private func link<Destination: View>(icon: String, label: String, destination: Destination) -> some View {
        return NavigationLink(destination: destination) {
            HStack {
                Image(systemName: icon)
                Text(label)
            }
        }
    }
}

Your appointment list view also contains NavigationLinks to the appointment detail views:

struct AppointmentListView: View {
    var body: some View {
        List {
            link(destination: AppointmentDetailView())
            link(destination: AppointmentDetailView())
            link(destination: AppointmentDetailView())
        }.navigationBarTitle("Appointments")
    }

    private func link<Destination: View>(destination: Destination) -> some View {
        NavigationLink(destination: destination) {
            AppointmentView()
        }
    }
}

Result: