public class MyList {
public List<T> list;
}
//Чтобы сохранить:
var listInClass = new MyList();
listInClass.list = myList
var outputString = JsonUtility.ToJson(listInClass);
PlayerPrefs.SetString("MY_LIST", outputString);
//Чтобы загрузить:
string globalDataJSON = PlayerPrefs.GetString("MY_LIST");
MyList loadedList = JsonUtility.FromJson<MyList >(globalDataJSON);