Place additional nodes when using smartdiagram

Question

I am trying to add additional nodes either side of a diagram produced using smartdiagram. Ideally, I would like node b1 placed to the left of the edge between a and b in the circular diagram, and b2 to the right of the edge between a and d. Using absolute coordinates to increase the distance between the additional nodes / try to place them still results in the circular diagram to the right of both nodes. Can this be done please?

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My example code

\documentclass[border=10pt]{standalone}
\usepackage{tikz, smartdiagram}
\usetikzlibrary{shapes.multipart}    
\tikzset{
state/.style={rectangle split, draw=black, text width=3cm}
}

\begin{document}

\begin{tikzpicture}[node distance = 4cm, auto]  
  \node [state, rectangle split parts=2] (b1) at (0,5) {text \nodepart{two} one};
  \node [state, rectangle split parts=2] (b2) at (5,5) {text \nodepart{two} two};
\end{tikzpicture}    

\smartdiagram[circular diagram] {a, b, c, d}  

\end{document}

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I thought maybe TikZ: adding nodes to a circular diagram from smartdiagram package could help but I can't see how to add the nodes i.e.

\smartdiagramadd[circular diagram]{a, b, c, d}{
              left of module1/\node [state, rectangle split parts=2]}

Answer 1

smartdiagram gives the nodes names. You can thus connect them using overlay. The IMHO only less appealing aspect of this is that things drawn in overlay mode do not increase the bounding box, which you need to do by hand. This explains the \hspace*{2cm} in

\documentclass[border=10pt]{standalone}
\usepackage{tikz, smartdiagram}
\usetikzlibrary{shapes.multipart}    
\tikzset{
state/.style={rectangle split, draw=black, text width=3cm}
}
\tikzset{every picture/.append style={remember picture}}
\begin{document}

\hspace*{2cm}\smartdiagram[circular diagram] {a, b, c, d}\hspace*{2cm}%
\begin{tikzpicture}[overlay]  
  \path (module1) -- (module2) node[midway,above left=1cm,state, rectangle split parts=2] (b1) at (0,5) {text \nodepart{two} one};
  \path (module1) -- (module4) node [midway,above right=1cm,state, rectangle split parts=2] (b2) at (5,5) {text \nodepart{two} two};
\end{tikzpicture}    


\end{document}