SortableDataObject::add_sortable_class('RelatedLink');

<?php
class RelatedLink extends DataObject
{
   static $db = array (
      'Title' => 'Text',
      'Address' => 'Text'
   );
   
   static $has_one = array (
      'Page' => 'Page'
   );
      
   public function getCMSFields_forPopup()
   {
      return new FieldSet(
         new TextField('Title'),
         new TextField('Address')
      );
   }
}
?>

$fields->addFieldToTab("Root.Content.RelatedLink", new DataObjectManager(
         $this,
         'RelatedLinks',
         'RelatedLink',
         array('Title' => 'Title','Address'=>'Address'),
         'getCMSFields_forPopup'
      ));

...
SortableDataObject::add_sortable_classes(array('Characteristic','Reference','Photo'));
...

<?php

class Characteristic extends DataObject
{
   static $db = array (
      'Label' => 'Text',
      'Value' => 'Text'
   );
   
   static $has_one = array (
      'DesignDetailsPage' => 'DesignDetailsPage'
   );
   
   public function getCMSFields_forPopup()
   {
      return new FieldSet(
         new TextField('Label',"Label (example: 'Length over all')"),
         new TextField('Value',"Value (example: '45.50 m')")
      );
   }

function PrincipalCharacteristics() {
if ($this->iteratorPos < 4) {
return true;
}
}

}

class Characteristic_Controller extends ContentController {
   
}

?>

...
static $has_many = array(
'Characteristics' => 'Characteristic',
'References' => 'Reference',
'Photos' => 'Photo'
);
...
      $manager2 = new DataObjectManager(
         $this, // Controller
         'Characteristics', // Source name
         'Characteristic', // Source class
         array(
            'Label' => 'Label',
            'Value' => 'Value'
         ), // Headings
         'getCMSFields_forPopup' // Detail fields (function name or FieldSet object)
         // Filter clause
         // Sort clause
         // Join clause
      );

      $fields->addFieldToTab('Root.Content.Characteristics', $manager2);
...