You should probably rather open an issue in pandoc-crossref (though I don't know if its a bug or just a question):
Otherwise here is a trick you may try:
If this is LaTeX the following might help:
1. Near the top of your markdown file or in a header-include[^1] put this:
\newenvironment{hideTable}{%
\let\toprule\relax%
\let\midrule\relax%
\let\bottomrule\relax%
}{}
\newenvironment{smallText}{\small}{}
I'm not sure about the exact font size command needed.
2. Where you want your side by side material use this:
`\begin{hideTable}`{=latex}
|
|-----------|-----------
|  | 
`\begin{smallText}`{=latex}
Fake caption text
`\end{smallText}`{=latex}
`\end{hideTable}`{=latex}
However note that these are non-floating images since last time I looked floating figures didn't work inside tables, and conversely captions don't work with non-floating images, so you might have to do some mysterious things to have this show up in your list of figures. I have only ever used this to place pieces of text and their translation side by side.
In HTML you might hide a table with CSS, i.e.
1. Where you want the side-by-side stuff:
:::hideTable
|
|-----------|-----------
|  | 
Fake caption text
:::
2. Arrange for some CSS which hides the table border to be included in your document header[^2], minimally:
div.hideTable table {
border-collapse: collapse;
}
Perhaps also
div.hideTable p {
text-size: small
}
Note that if you have other CSS in effect which e.g. sets background colors or borders on table rows you will need to disable that too.