Hi
Currently this is not possible out of the box, but fortunately you can relatively easily modify the scripts to do this.
In the NodeLink2.cs script you will find two lines that look like this
// Create new nodes on the point graph
if (startNode == null) startNode = AstarPath.active.data.pointGraph.AddNode((Int3)StartTransform.position);
if (endNode == null) endNode = AstarPath.active.data.pointGraph.AddNode((Int3)EndTransform.position);
after those lines you can assign tags to those nodes
startNode.Tag = ...;
endNode.Tag = ...;