Named slots are awesome, they allow e.g. defining table columns inside a html.heex file like

<.table items={items}>
<:col let={f} field={:title}>...></:col>
</.table>

I want to write a reusable wrapper to allow selecting multiple table entries for bulk operations.
To achieve this, an additional column-slot is added to the list of columns and handed forward to the real table-render function.

@impl Phoenix.LiveComponent
def render(assigns) do
  edit_col = %{
      label: "",
      field: :select,
      inner_block: fn _changed, argument ->
        assigns = assign(assigns, id: argument.id)

        ~H"""
        <button rel="toggle-select" phx-click="toggle-select" phx-value-id={@id} phx-target={@myself}> 
          <input type="checkbox" checked={MapSet.member?(@selected, @id)} />
        </button>
        """
      end,
      __slot__: :col
    }
      assigns
      |> assign(:col, [edit_col | assigns.col])
      |> FlopComponents.table()
      end

This works, but edit_col is created using the private API.

Is there a better way to create a named slot inside Elixir-Code - like a pre-defined function slot that can be used instead?