More leeway in defining how footnotes are rendered

[10b14224cc]

I have devised a way to print a newline in latex output through the use of makecell, but now I need to control how the footnote is printed.

In particular, this is the latex output I currently obtain:

\makecell{\textbf{Drug A} \\ N = 98}\textsuperscript{\textit{1}}

I would like to put the footnote inside the makecell.

But I see that opt_footnote_spec has limited capabilities and wouldn't allow me to do that.