public class ApplicationActionBarAdvisor extends ActionBarAdvisor {
//...

	protected void fillCoolBar(ICoolBarManager coolBar) {
		ToolBarManager toolBarManager = new ToolBarManager( coolBar.getStyle() );
		toolBarManager.add( fileOpenAction );
		coolBar.add(toolBarManager);
		coolBar.add( new GroupMarker( TOOLB_ADDITIONS )); 

	}
}

public class EditorContribCastle extends MultiPageEditorActionBarContributor {

	@Override
	public void contributeToCoolBar(ICoolBarManager coolBarManager) {
		
		ToolBarManager toolBarManager = new ToolBarManager(coolBarManager.getStyle());
		
		toolBarManager.add(actionX);

		ToolBarContributionItem tbmi = new ToolBarContributionItem(toolBarManager);

		SubCoolBarManager sbm = (SubCoolBarManager)coolBarManager;

		// this line does not work
		coolBarManager.insertBefore(ApplicationActionBarAdvisor.TOOLB_ADDITIONS, tbmi);

		// this line does not work
		coolBarManager.appendToGroup(ApplicationActionBarAdvisor.TOOLB_ADDITIONS, tbmi );

		// this line work!!
		sbm.getParent().insertBefore(ApplicationActionBarAdvisor.TOOLB_ADDITIONS, tbmi);
		
		// this line appends to wrong position
		sbm.getParent().appendToGroup(ApplicationActionBarAdvisor.TOOLB_ADDITIONS, tbmi);
		
	}
}