Customizing the metamodel : Metamodel graphical editor : Enabling the metamodel object
  
Enabling the metamodel object
1 Select Tools > Customize Method Support.
2 In the System Architect Property Configuration dialog, click the Advanced button to open the advanced Configure Property Set window.
3 In the Configure Property Set window, on the bottom left list of Available Property Sets, find, select, and add the Meta Model Objects choice to the list of Selected Property Sets on the right. Click OK to close the dialogs and reopen the encyclopedia for the changes to take effect.
Result