in query metadata you can have something like:

                    <item text="More Actions" insertPosition="end">
                        <item text="Jump To History">
                            <onClick>
                                historyHandler(dataRegion, dataRegionName);
                            </onClick>
                        </item>
                        <item text="Jump To Other Dataset">
                            <onClick>
                                datasetHandler(dataRegion, dataRegionName);
                            </onClick>
                        </item>
                    </item>

Is there any way to make either the top level button or menu items disabled by default? This is not the same as 'requiresSelection'. The rationale for disabling by default would be for the onLoad JS code to enable the menu item as needed. The alternative would be not to have a menu item at all, and for the onLoad code to create one if appropriate.