\setupinteraction[state=start]

\definereferenceformat [intesta] [left=(,right=),text=Whatever~,style=\sl,color=black]
\definereferenceformat [intestb] [left=(,right=),label=figure]

\starttext

\placeformula[x]\startformula a \stopformula

\starttabulate[|||||]
\NC \in     [x] \NC \in     {left}[x] \NC \in     {}{right}[x] \NC \in     {left}{right}[x] \NC \NR
\NC \intesta[x] \NC \intesta{left}[x] \NC \intesta{}{right}[x] \NC \intesta{left}{right}[x] \NC \NR
\NC \intestb[x] \NC \intestb{left}[x] \NC \intestb{}{right}[x] \NC \intestb{left}{right}[x] \NC \NR
\stoptabulate

% \in     [x] \quad \in     {left}[x] \quad \in     {}{right}[x] \quad \in     {left}{right}[x] \par
% \intesta[x] \quad \intesta{left}[x] \quad \intesta{}{right}[x] \quad \intesta{left}{right}[x] \par
% \intestb[x] \quad \intestb{left}[x] \quad \intestb{}{right}[x] \quad \intestb{left}{right}[x] \par

\stoptext
