in method edit_entry()

mcp.freeform.php

		if ($form_data['field_order'] !== '')
		{
			$order_ids = $this->actions()->pipe_split($form_data['field_order']);

			if ( ! empty($order_ids))
			{
				//this makes sure that any fields in 'fields' are in the
				//order set as well. Will add missing at the end like this
				$field_loop_ids = array_merge(
					$order_ids,
					array_diff($field_loop_ids, $order_ids)
				);
			}
        }
        $layout = $this->composer_field_order( ee()->input->get('form_id') );

        if ( $layout && empty($order_ids) ) {
            $field_loop_ids = array_merge( $layout , array_diff( $field_loop_ids , $layout ) );
        }