Yep, there is a bit to it so I’m not going to write everything out but here is a fairly typical high-level design of this:

defmodule MyApp.Quotes.Quote do
  use Ecto.Schema

  schema "quotes" do
    # ...
    has_many :items, MyApp.Quotes.Items
    # ...
  end

  def changeset(q, attrs) do
    q
    |> cast(attrs, [...])
    |> cast_assoc(:items)
end

defmodule MyApp.Quotes.Item do
  use Ecto.Schema

  schema "quote_items" do
    # ...
    belongs_to :quote, MyApp.Quotes.Quote
    # ...
  end

  def changeset(item, attrs) do
    item
    |> cast(attrs, [...])
  end
end

defmodule MyApp.Quotes do
  def change_quote(q \\ %MyApp.Quotes.Quote{}, attrs \\ %{}) do
    MyQpp.Quotes.Quote.changeset(q, attrs)
  end

  def create_quote(attrs) do
    %MyApp.Quotes.Quote{}
    |> change_quote(attrs)
    |> MyApp.Repo.insert()
  end
end

defmodule MyAppWeb do
  use MyAppWeb, :live_view

  def mount(_params, _session, socket) do
    changeset = MyApp.Quotes.change_quote()

    {:ok, assign(socket, :form, to_form(changeset)}
  end

  def render(assigns) do
    ~H"""
    <.simple_form for={@form} phx-submit="...">
      <.inputs_for :let={item} field={@form[:items]}>
        <%!-- item stuff --%>
      </.input_for>
    </.simple_form>
    """"
  end
end

Again, very high level. Also note, I’m using q as a variable since quote is one of very few reserved words in Elixir.

This is a great blog post to learn more.

As far as LiveComponents go, they work the same as function components in this regard and you shouldn’t really need one for items. LiveComponents really aren’t necessary for forms and I don’t love that the generators use them, especially since the docs say to not overuse LiveComponents. I think it’s more for an example of how to use them but I’m not sure.