Hello, I’d like to being able to preview chemfig, like lines beginning
with \chemfig{.

But (a) they’re not detected as LaTeX fragments by the previewer (and it
seems only some matchers are accepted by default, I can’t say, for
instance, “^{\\[a-zA-Z]*[a-zA-Z0-9 ].*}$”), and (b) when previewing I
don’t see any way to include packages, like “\usepackage{chemfig}”, so
that even “\begin{flushleft}<\n>\chemfig{O=O}<\n>\end{flushleft}”, for
instance, doesn’t work.

Is there any way to do this? Otherwise, how could I fix it? Which part
of org-mode to hack? Could this be improved for next release?