I can't sort items out of group

[Nekiess]

I have a table like the one below, I have items outside groups and 1 group, I can get items that are inside group and put outside this group but I can't get items and add to group, how to add items to group?
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The HTML:
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A Column
A Item 1
A Item 2
A Item 3
A Item 4
A Item 5 A Item 5.1 A Item 5.2 A Item 5.3 A Item 5.4
A Item 6

. . . . The JavaScript

<script type="text/javascript">

  $(function  () {
  	$('.sorted_table').sortable({
  		  containerSelector: 'table',
  		  itemPath: '> tbody',
  		  itemSelector: 'tr',
  		  placeholder: '<tr class="placeholder"/>'
  		});			
  });

  </script>

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