How do I copy an already existing field in manage display?
The approach I would use would be to use a custom php snippet in a block to pull the field value out of $node and to format the field. I would then place the block in a region of the page where I needed it. 


&lt;?php

if (arg(0) == 'node' &amp;&amp; is_numeric(arg(1))) {

$node = node_load(arg(1));

if (isset($node->field_node_reference['und'])) {

foreach ($node-&gt;field_node_reference['und'] as $other_node) {
  $link = '/node/' . $other_node['node']-&gt;nid;
  $title = $other_node['node']-&gt;title;
  print (l( $title, $link));
}


}

} ?> 


This would be the core code for a node reference field. You should pretty it up to format your display, but this gets the information on your page a second time.