\definebtxdataset
[chemistry]

\usebtxdataset
[chemistry] [C6H6O.bib]

\setupbtx
  [specification=chemistry,
   dataset=chemistry]
   
\definebtxrendering
  [chemistry]
  [specification=chemistry,
   group=chemistry,
   dataset=chemistry]
   
\startsetups btx:chemistry:list:chemical
    \startframed [frame=off,location=middle]
        \bTABLE [frame=off]
        	\bTR
        	\bTD [width=.2\textwidth,ny=2]
        	\goto
        		{\startchemical [scale=small]
        			\chemical [\btxflush{chemical}] \stopchemical} [program(\btxflush{rendered})]
        		\eTD
        		\bTD [width=.2\textwidth] \chemical{\btxflush{formula}} \eTD \bTD [width=.4\textwidth] \btxflush{iupac} \eTD
        		\eTR \bTR
        		\bTD \btxflush{mw}~g/mole \eTD
        		\bTD \btxflush{cas} \eTD \eTR
        \eTABLE
    \stopframed
\stopsetups

% the following setupbtx gets ignored

\definebtx[chemistry:cite:formula]
[
	left={\color[blue]{(}},
	right={\color[red]{)}},
	inbetween={\btxcomma\btxspace},  % no effect
]

%\setupbtx
%	[chemistry:cite:formula]
%	[
%	left={(},
%	right={)},
%	separator:2={\btxcomma\btxspace},
%		separator:3={\btxcomma\btxspace},
%			separator:4={\btxcomma\btxspace},
%	]

\startsetups btx:chemistry:cite:formula
	\chemical {\currentbtxfirst}
\stopsetups

\startsetups btx:chemistry:cite:chemical 
	\startchemical [scale=600]
		\chemical [\currentbtxfirst] 
	\stopchemical
\stopsetups

\starttext
% works as per manual
\placebtxrendering [method=dataset]

% works as per manual
\cite [name][108-95-2]|<|or|>|
\cite [formula][108-95-2]|<|or|>|
\cite [chemical][108-95-2]|<|or|>|
\cite [molarvolume] [108-95-2]

% works as per manual
\cite [name][566-33-5]|<|or|>|
\cite [formula][566-33-5]|<|or|>|
\cite [chemical][566-33-5]|<|or|>|
\cite [molarvolume] [566-33-5]

% added multiple references ; no inbetween= appears
\cite [name][108-95-2,566-33-5]\par
\cite [formula][108-95-2,566-33-5]\par
\cite [chemical][108-95-2,566-33-5]\par
\cite [molarvolume][108-95-2,566-33-5]\par

\stoptext