title: Custom node and links in .dgml editor/viewer
body: <p>I am trying to use Visual Studio DGML viewer / editor to build a directed graph. I would like to be able to add nodes and links with pre-defined custom properties. As of now, if I right click on the DGML document, I can add a Generic Node with no custom properties. Even if I assigned a Category to this node, I don't seem to be able to add a custom property to this node. I tried to do it outside of Visual Studio using the GraphModel. It works but the only viewer available is Visual Studio, hence each time I add a nodes programmatically, VS asks me if I want to reload the modified .dgml file, annoying... </p>
  
  <p>So is there a way to add custom node / link to a .dgml graph within Visual Studio ?</p>