\usemodule[article-basic]

\setupbodyfont[dejavu]

\starttext

\setupboxanchorcontent
  [top,left]
  [rulecolor=darkyellow]

\setupboxanchorcontent
  [bottom,right]
  [rulecolor=darkblue]

\input tufte

$
    \connectboxanchors[top][top]{one}{two}
    x + \frac[source=\namedboxanchor{one}]{1+x}{2-x} =
    z + \frac[source=\namedboxanchor{two}]{1+x^2}{2-x^3}
$

\input ward


\connectboxanchors[top][top]{one}{two}

So how about
$
    x + \frac[source=\namedboxanchor{one}]{1+x}{2-x}
$
and
$
    z + \frac[source=\namedboxanchor{two}]{1+x^2}{2-x^3}
$
then. Of course we need to handle page crossing then.

\connectboxanchors[top][top]        {one}{two}
\connectboxanchors[top][top][dash=1]{three}{four}

And can we do
$
%     \showboxes
    x + \frac{1 \mathboxanchored{one}{+} x \mathboxanchored{three}{-} z}{2-x}
$
and
$
%     \showboxes
    z + \frac{1 \mathboxanchored{two}{+} x^2 \mathboxanchored{four}{-} z}{2-x^3}
$
to be more granular?

\blank[2*big]

\connectboxanchors[top]   [top]   [text={\small\small\strut\bf watch}]{one}  {two}
\connectboxanchors[bottom][bottom][text={\small\small\strut\bf out}]  {three}{four}

And can we do
$
%     \showboxes
    x + \frac{1 \mathboxanchored{one}{+} x - z}{2 \mathboxanchored{three}{-} x}
$
and
$
%     \showboxes
    z + \frac{1 \mathboxanchored{two}{+} x^2 - z}{2 \mathboxanchored{four}{-} x^3}
$
to be more granular?

\stoptext