In Microsoft Dynamics AX 2012, relations can no longer be created under extended data type (EDT) nodes in the Application Object Tree (AOT). In a table browser

 -          The “view details” option only works with views in when there is a relation defined in the EDT (in the Relations node). We don't look at the table relations to figure out the relation from a view field or looking at the “Table References” node.
 
-          The scenario will have worked in AX 2009, but this needs to be migrated in correctly in AX 2012 (meaning the EDT relation was moved to the table and the SourceEDT property of the table relation was correctly set).
 
-          If the EDT relation was not correctly migrated, or this is a new EDT (in which you cannot define a relation anymore), the “view details” will not work. You can make it work by creating the relation in the table and set the SourceEDT to the EDT of the field.
 

For further reference please see http://msdn.microsoft.com/en-us/library/gg989788.aspx