[Neos] start node for content menu

[Dominic Garms]

Hello

I would like to use a special menu and tried to simply extend the 
existing NodeType of menu with a startNode property:


'DMF.BasePackage:ProjectMenu':
   superTypes: ['TYPO3.Neos.NodeTypes:Menu']
   ui:
     label: 'Project menu'
   properties:
     'startNode':
       type: reference
       ui:
         label: 'Starting node'
         inspector:
           group: 'options'


prototype(DMF.BasePackage:ProjectMenu) < 
prototype(TYPO3.Neos.NodeTypes:Menu) {
     node = ${q(node).property('startNode') || q(node)}
}

But this approach is not working, does anyone see a mistake or is this 
not possible at the moment?

Thanks,

Dominic