The ‘currentChildGraph’ property has been basically replaced with two new methods those being ‘GetCurrentChildGraph()’ and ‘SetCurrentChildGraphAssignable(IGraphAssignable assignable)’.
The ‘IGraphAssignable’ parameter of the ‘SetCurrentChildGraphAssignable’ method, is basically the node which contains the SubGraph (all nodes containing a subgraph are IGraphAssignables).
Having said that, both of those methods are ‘internal’. If you want to use them please change their access modifier to ‘public’. I can also make them public for the next version if this is something you will be using.