I'm trying to customise \cite and unable to get inbetween= to appear between entries in a multi-ref citation.

My own customisations via a copy of publ-imp-apa.mkvi and .lua have this problem, so in case it was due to my customisation I went back to solid ground — the Chemistry example, pp. 70-74 in the Publications manual (http://pragma-ade.nl/general/manuals/mkiv-publications.pdf).

The cite examples on p.74 work as shown, but when I add each of the following:

\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][108-95-2,566-33-5,24599-57-3]\par

I simply get the citation details, no separator between, and no left or right.

Either of the following works for left= and right=. However inbetween= does not activate, and similarly for separator:2, separator:3, separator:4.

\definebtx [chemistry:cite:formula]
[left={\color[blue]{(}}, % the colour to differentiate from \setupbtx below
 right={\color[red]{)}},
 inbetween={\btxcomma\btxspace},  % no effect
]

\setupbtx [chemistry:cite:formula]
[left={(},
 right={)},
 inbetween={\btxcomma\btxspace},
]

Grateful for any guidance as to how I can remedy this issue.

Regards, and thanks,

Mike