I received an answer from Allegorithmic which explains what I was doing wrong and how to connect the nodes normally.
Thanks for reporting this issue. The connection problem happens because of the material modes (standard and compact). If you hit the 1 key to place the graph in standard mode, you can make the connection.
I seem to have come across a bug in Substance Designer’s Curvature Node, which I have reported to Allegorithmic so it may be resolved by the time you read this.
The last months I have been working through the tools on Allegorithmic’s Substance Painter and Substance Designer and how to use it in conjunction with Blender 3D
So far the main conclusion I have come to is it works and works pretty well, there are a couple of caveats though, these I will go into perhaps in a later post. The main thing though I will mention here is to ensure you export the model in either OBJ or preferably FBX (the reason for this is OBJ doesn’t update in Substance Designer automatically).
Substance Designer can be set up to auto save every few minutes in case of a crash, which is something that happens a lot to me at least.
The problem is I couldn’t find the auto save files no matter how I tired they weren’t in any of the obvious folders, including the /tmp folder which would be logical.
So I did a little web search and found that the programmers in their infinite wisdom decided to put the back ups in a .