Всё что показывается на видео - рання работа, которую Google официально не показывала и всё может измениться!

 // Создаем SavedState с помощью DSL:
  val savedState = savedState {
    putInt("currentPage", 1)
    putString("filter", "favorites")
  }

val currentPage = savedState.read { getInt("currentPage") }
savedState.write { remove("currentPage") }

@Serializable
data class Person(val firstName: String, val lastName: String)

fun main() {
    val person = Person("John", "Doe")
    val encoded: SavedState = encodeToSavedState(person)
    val decoded: Person = decodeFromSavedState(encoded)
}

class MyActivity : ComponentActivity() {
    var person by saved { Person("John", "Doe") }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        this.person = Person("Jane", "Doe")
    }
}

class MyViewModel(handle: SavedStateHandle) : ViewModel() {
    var person by handle.saved { Person("John", "Doe") }

    fun onPersonChanged(person: Person) {
        this.person = person
    }
}