Trying to pass a Binding<Bool> variable into a view?

It is not really clear what you want to achieve, but have a look at the code below:

import SwiftUI

struct ParentView: View {

    @Binding var customVariable: Bool

    var body: some View {
        VStack {
            Toggle(isOn: $customVariable) {
                Text("Show/Hide Custom View")
            }
            if $customVariable.wrappedValue {
                CustomView(customVariable: $customVariable)
            }
        }
    }
}

struct CustomView: View {

    @Binding var customVariable: Bool

    init(customVariable: Binding<Bool>) { // You don't need an initializer here, it is just to demonstrate how you can use it for Binding values
        _customVariable = customVariable
    }

    var body: some View {
        Text("Custom View")
    }
}

However, a better way to coordinate the model and the view in SwiftUI can be illustrated as below:

import SwiftUI

class CustomModel: ObservableObject {

    @Published var shouldShowCustomView: Bool = false
}    

struct ParentView: View {

    @ObservedObject var model: CustomModel

    var body: some View {
        VStack {
            Toggle(isOn: $model.shouldShowCustomView) {
                Text("Show/Hide Custom View")
            }
            if model.shouldShowCustomView {
                CustomView()
                    .environmentObject(model)
            }
        }
    }
}

struct CustomView: View {

    @EnvironmentObject var model: CustomModel

    var body: some View {
        Text("Custom View")
    }
}

So, instead of Binding, you can use ObservableObject with Published values.