不使用FormBuilder访问fields_for中的嵌套模型属性

I have a Rails form that is being used for creating and editing a model with a has_many relationship. I'm very familiar with typical forms with nested models, but my current problem requires accessing rendering some form elements using typical FormBuilder helpers and other HTML elements using data from the model itself. For example, my top level form has something like:I have a Rails form that is being used for crea