I'm having trouble scaling down symbols and emojis. For a while I assumed
these don't scale with the current font size. Then I scoured the mailing
list and realized that while scaling down seems broken, scaling up works as
expected:


\usesymbols[mvs]

\setupsymbolset[martinvogel 2]

%\showallmakeup

\starttext
% Progressively larger as expected.
\symbol[ShortForty]
{\tfa\symbol[ShortForty]}
{\tfb\symbol[ShortForty]}
{\tfc\symbol[ShortForty]}
{\tfd\symbol[ShortForty]}

% Unexpectedly all the same size.
\symbol[ShortForty]
{\tfx\symbol[ShortForty]}
{\tfxx\symbol[ShortForty]}

% This works, but why? Isn't \small just a synonym for \tfx via
% \definealternativestyle? Anyway there is no synonym for \tfxx.
\symbol[ShortForty]
{\switchtobodyfont[small]\symbol[ShortForty]}
{\small\symbol[ShortForty]}

% This also works but is less than ideal when matching surrounding font
sizes.
% Which factor should I use to match \tfxx?
\symbol[ShortForty]
\scale[factor=4]{\symbol[ShortForty]}

% Same as above comment, more or less.
\symbol[ShortForty]
{\switchtobodyfont[5pt]\symbol[ShortForty]}
\stoptext


* MWE for builtin symbols; emojis require local fonts. I assume whichever
solution would apply equally to either.

thanks,