pandoc-crossref-0.3.15.0: test/m2m/subfigures/expect.md
You can define subfigures:
::: {#fig:subfigures .figure .subfigures}
{#fig:subfig1} {#fig:subfig2} 
{#fig:subfig4}  {#fig:subfig6}
{#fig:subfig7}  {#fig:subfig9}
::: caption
Figure 1: Caption. a --- 1, b --- 2, c --- 3, d --- 4, e --- 5, f --- 6,
g --- 7, h --- 8, i --- 9
:::
:::
::: {#fig:subfigures2 .figure .subfigures}
::: {#fig:subfig21 .figure}

::: caption
a
:::
:::
::: {#fig:subfig22 .figure}

::: caption
b
:::
:::
::: figure

::: caption
c
:::
:::
::: {#fig:subfig24 .figure}

::: caption
d
:::
:::
::: figure

::: caption
e
:::
:::
::: {#fig:subfig26 .figure}

::: caption
f
:::
:::
::: {#fig:subfig27 .figure}

::: caption
g
:::
:::
::: figure

::: caption
h
:::
:::
::: {#fig:subfig29 .figure}

::: caption
i
:::
:::
::: caption
Figure 2: Caption. a --- 1, b --- 2, c --- 3, d --- 4, e --- 5, f --- 6,
g --- 7, h --- 8, i --- 9
:::
:::
Figures themselves can be referenced fig. 2, as well as individual
subfigures: figs. 1 (a), 1 (b), 2 (i)