InsertArrayItemButtonField

type InsertArrayItemButtonField = Omit<MatButtonField<InsertArrayItemEvent>, 'event' | 'type' | 'eventArgs'> & {
  type: 'insertArrayItem';
  /**
   * The key of the array field to insert items into.
   * Required when the button is placed outside the array.
   * When inside an array, this is automatically determined from context.
   */
  arrayKey?: string;
  /**
   * The index at which to insert the new item.
   */
  index: number;
  /**
   * Template for the new array item. REQUIRED.
   * - Single field (ArrayAllowedChildren): Creates a primitive item (field's value is extracted directly)
   * - Array of fields (ArrayAllowedChildren[]): Creates an object item (fields merged into object)
   */
  template: ArrayAllowedChildren | readonly ArrayAllowedChildren[];
};