View.swift

struct Collapsable<Content: View>: View {
  @State var collapsed: Bool = true
  let content: () -> Content

  init(@ViewBuilder content: @escapin () -> Content) {
    self.content = content
  }

  var body: some View {
    VStack {
      if !collapsed {
        content() // <--- Expand when body is called
      }
      Button(collapsed ? "↓ open" : "↑ close") {
        visible.toggle()
      }
    }
  }
}