Variable for DestinationView

When you post code, please post more so that we can better explain the solution.

So, show how stasSigns is defined and how each zodiacSign is defined in this structure.

A typical pattern would be:

struct ContentView : View {
        @ViewBuilder func destination(name: String) -> some View {
            switch name {
                case "aries": AriesView()
                // other case here
                default: EmptyView()
              }
          }

    var body: some View {
            List {
                ForEach(starSigns) {zodiacSign in  // zodiacSign should start with lowercase, as it is an instance
                    NavigationLink(destination: destination(name: zodiacSign.name)) {// destinationView should start with lowercase, as it is a property
                        HStack {
                            Text(zodiacSign.Symbol)
                            Text(zodiacSign.name)
                        }
                    }
                }
            }
}

struct ZodiacSign: Identifiable {
    let id = UUID()
    var name: String
    var Symbol: String
    var DestinationView: View
}

var starSigns = [
    ZodiacSign(name: "Aries", Symbol: "♈︎", DestinationView: AriesView()),
    ZodiacSign(name: "Taurus", Symbol: "♉︎", DestinationView: TaurusView()),
    ZodiacSign(name: "Gemini", Symbol: "♊︎", DestinationView: GeminiView()),
    ZodiacSign(name: "Cancer", Symbol: "♋︎", DestinationView: CancerView()),
    ZodiacSign(name: "Leo", Symbol: "♌︎", DestinationView: LeoView()),
    ZodiacSign(name: "Virgo", Symbol: "♍︎", DestinationView: VirgoView()),
    ZodiacSign(name: "Libra", Symbol: "♎︎", DestinationView: LibraView()),
    ZodiacSign(name: "Scorpio", Symbol: "♏︎", DestinationView: ScorpioView()),
    ZodiacSign(name: "Sagittarius", Symbol: "♐︎", DestinationView: SagittariusView()),
    ZodiacSign(name: "Capricorn", Symbol: "♑︎", DestinationView: CapricornView()),
    ZodiacSign(name: "Aquarius", Symbol: "♒︎", DestinationView: AquariusView()),
    ZodiacSign(name: "Pisces", Symbol: "♓︎", DestinationView: PiscesView())
]

struct ContentView: View {
    var body: some View {
        VStack {
            List {
                ForEach(starSigns) {ZodiacSign in
                    NavigationLink(destination: ZodiacSign.DestinationView) {
                        Text(ZodiacSign.Symbol)
                        Text(ZodiacSign.name)
                    }
                }
            }
        }
    }
}

struct AriesView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct TaurusView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct GeminiView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct CancerView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct LeoView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct VirgoView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct LibraView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct ScorpioView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct SagittariusView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct CapricornView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct AquariusView: View {
    var body: some View {
        VStack {
            
        }
    }
}

struct PiscesView: View {
    var body: some View {
        VStack {
            
        }
    }
}

This is the full code, line 5 is where I was referring to earlier, I would like to add the destination in each one, please could you explain how I would do this.

I would do it this way with ViewBuilder:

struct ZodiacSign: Identifiable {
    let id = UUID()
    var name: String
    var symbol: String      // as per Swift conventions, should start with lowercase
    // Replaced by ViewBuilder  var DestinationView: View
}

@ViewBuilder func zodiacDestination(name: String) -> some View {
    switch name {
        case "Aries"    : AriesView()
        case "Taurus"   : TaurusView()
        case "Gemini"   : GeminiView()
        case "Cancer"   : CancerView()
        case "Leo"      : LeoView()
        case "Virgo"    : VirgoView()
        case "Libra"    : LibraView()
        case "Scorpio"  : ScorpioView()
        case "Sagittarius": SagittariusView()
        case "Capricorn": CapricornView()
        case "Aquarius" : AquariusView()
        case "Pisces"   : PiscesView()
        default: EmptyView()
      }
  }

struct ContentView: View {

    @State var starSigns = [    // Need to be a State var
        ZodiacSign(name: "Aries", symbol: "♈︎"),  // DestinationView: AriesView()),
        ZodiacSign(name: "Taurus", symbol: "♉︎"), // DestinationView: TaurusView()),
        ZodiacSign(name: "Gemini", symbol: "♊︎"), // DestinationView: GeminiView()),
        ZodiacSign(name: "Cancer", symbol: "♋︎"), // DestinationView: CancerView()),
        ZodiacSign(name: "Leo", symbol: "♌︎"), // DestinationView: LeoView()),
        ZodiacSign(name: "Virgo", symbol: "♍︎"), // DestinationView: VirgoView()),
        ZodiacSign(name: "Libra", symbol: "♎︎"), // DestinationView: LibraView()),
        ZodiacSign(name: "Scorpio", symbol: "♏︎"), // DestinationView: ScorpioView()),
        ZodiacSign(name: "Sagittarius", symbol: "♐︎"), // DestinationView: SagittariusView()),
        ZodiacSign(name: "Capricorn", symbol: "♑︎"), // DestinationView: CapricornView()),
        ZodiacSign(name: "Aquarius", symbol: "♒︎"), // DestinationView: AquariusView()),
        ZodiacSign(name: "Pisces", symbol: "♓︎") // DestinationView: PiscesView())
    ]

    var body: some View {
        // VStack {
        NavigationView { // You have to put in a NavigationView
            List {
                ForEach(starSigns, id: \.id) {zodiacSign in   // should start with lowercase
                    NavigationLink(destination: zodiacDestination(name: zodiacSign.name)) {
                        Text(zodiacSign.symbol)
                        Text(zodiacSign.name)
                    }
                }
            }
        }
    }
}

struct AriesView: View {
    var body: some View {
        VStack {
            Text("♈︎ Aries is a constellation…")
        }
    }
}

struct TaurusView: View {
    var body: some View {
        VStack {
            Text("♉︎ Taurus is a constellation…")
        }
    }
}

struct GeminiView: View {
    var body: some View {
        VStack {
            Text("♊︎ Gemini is a constellation…")
        }
    }
}

To add to @Claude31 point, since you have a custom data type ZodiacSign, you could use value based navigation where you associate a view with a kind of data, and then present a value of that data type from a navigation link using the navigationDestination(for:destination:) modifier.

I would recommend you have a look at Migrating to new navigation types article, it contains various examples of programmatic navigation.

Thank you for the help, it works now!!! :D