Yes, thanks, but this would change the behavior for all propertygrids in my application.

I just did a little change, that the datagrid-groups can only be opened exclusively:

onLoadSuccess: function() {

   var groupcount = 5;
   // Just use the correct number here ...
   // in Version 1.4.4 you can get the count via 'groups' method

   $(this).propertygrid('collapseGroup');
   $(this).propertygrid('expandGroup',0);

   var dg=this;
   $(this).parent().find('.datagrid-row-expander').on('click', function() {
      group=$(this).parents('.datagrid-group').attr('group-index');
      for(var i=0;i<groupcount;i++) {
         if(i!=group) {
            $(dg).propertygrid('collapseGroup', i);
         }
      }
   });
}

Why don't you just resize the Tab after you have added the new content?