Set the Navigation Bar Title Font with 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:

For some reason, SwiftUI requires that you also set .navigationBarTitle for .navigationBarHidden to work properly.

NavigationView {
    FileBrowserView(jsonFromCall: URLRetrieve(URLtoFetch: applicationDelegate.apiURL))
        .navigationBarTitle("")
        .navigationBarHidden(true)
}

Update

As @Peacemoon pointed out in the comments, the navigation bar remains hidden as you navigate deeper in the navigation stack, regardless of whether or not you set navigationBarHidden to false in subsequent views. As I said in the comments, this is either a result of poor implementation on Apple's part or just dreadful documentation (who knows, maybe there is a "correct" way to accomplish this).

Whatever the case, I came up with a workaround that seems to produce the original poster's desired results. I'm hesitant to recommend it because it seems unnecessarily hacky, but without any straightforward way of hiding and unhiding the navigation bar, this is the best I could do.

This example uses three views - View1 has a hidden navigation bar, and View2 and View3 both have visible navigation bars with titles.

struct View1: View {
    @State var isNavigationBarHidden: Bool = true

    var body: some View {
        NavigationView {
            ZStack {
                Color.red
                NavigationLink("View 2", destination: View2(isNavigationBarHidden: self.$isNavigationBarHidden))
            }
            .navigationBarTitle("Hidden Title")
            .navigationBarHidden(self.isNavigationBarHidden)
            .onAppear {
                self.isNavigationBarHidden = true
            }
        }
    }
}

struct View2: View {
    @Binding var isNavigationBarHidden: Bool

    var body: some View {
        ZStack {
            Color.green
            NavigationLink("View 3", destination: View3())
        }
        .navigationBarTitle("Visible Title 1")
        .onAppear {
            self.isNavigationBarHidden = false
        }
    }
}

struct View3: View {
    var body: some View {
        Color.blue
            .navigationBarTitle("Visible Title 2")
    }
}

Setting navigationBarHidden to false on views deeper in the navigation stack doesn't seem to properly override the preference of the view that originally set navigationBarHidden to true, so the only workaround I could come up with was using a binding to change the preference of the original view when a new view is pushed onto the navigation stack.

Like I said, this is a hacky solution, but without an official solution from Apple, this is the best that I've been able to come up with.