The shortcoming identified by the OP is a bit more complex. Consider the 
need to hyphenate an item title. Hyphenation should be done according to 
the rules of the language involved.

If the item title has internal quotation marks, it may be important to 
ensure that those also agree with the language of the item title.

This is not an unusual when dealing with such things as the proceedings of 
international conferences. Iterated manual tuning may be the only option if 
a good result is required and there is no mechanism to specify a language 
for each item. 

-- 
Rik

On Wednesday, October 13, 2021 at 11:05:36 AM UTC-4 denis...-NSENcxR/0n0@public.gmane.org wrote:

> True, there's not way to set the language of individual fields.
> But there's still an easier solution: set the language of the particular 
> item to something other than english (e.g. German) and title case the 
> chapter title manually.
>
> Denis
>
> > -----Ursprüngliche Nachricht-----
> > Von: pandoc-...-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org <pandoc-...-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org>
> > Im Auftrag von Bastien DUMONT
> > Gesendet: Mittwoch, 13. Oktober 2021 16:58
> > An: pandoc-...-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
> > Betreff: Re: Different container and item languages
> > 
> > There is no way to set the language of individual items or fields in 
> CSL. You will
> > have to use a modified version of your style file (*.csl) where you 
> remove all
> > `text-case="title"` or `text-case="capitalize-all"` attributes. Then, 
> you will have
> > to capitalize your titles by hand in Zotero.
> > 
> > More informations here about how to write or modify a style:
> > https://www.zotero.org/support/dev/citation_styles
> > 
> > Le Wednesday 13 October 2021 à 07:36:28AM, jmuc...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org a écrit :
> > > (I would have thought this would have come up before, but I haven't
> > > been able to find a thread on it.)
> > >
> > > I have a number of book sections that are in one language, when the
> > > book that contains them is titled in another. When the book's language
> > > is not English, but the section's is, this results in the book title
> > > getting capitalized according to English rules and not those of the 
> language
> > (say, German).
> > >
> > > Is there any way around this? I don't see anything like
> > > "container-language" in csljson, which I'm exporting from Zotero to 
> get my
> > biblio file.
> > >
> > > TIA.
> > >
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> > >
> > > References:
> > >
> > > [1] mailto:pandoc-discus...-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
> > > [2]
> > > https://groups.google.com/d/msgid/pandoc-discuss/38c03aca-c194-4a4d-8e
> > > 10-
> > 55e394056b3fn%40googlegroups.com?utm_medium=email&utm_source=foote
> > r
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>

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