The ToString command converts the given script object to an XML string that can be used as the return value of a button-press in Maple Learn.

$\mathrm{with}\left(\mathrm{DocumentTools}:-\mathrm{Canvas}\right)\:$

Complexify := proc( canvas )
    uses DC=DocumentTools:-Canvas;
    randomize();
    local script := DC:-Script();
    for local m in DC:-GetMath(canvas,'inert') do      # get all the math in the canvas
        SetActive(script,m);       # set the location of the annotation
        local newexpr := RandomTools:-RandomExpand(m:-math);
        SetMath(script,newexpr);
   end do;
   ToString(script);
end proc:

$\mathrm{cv}≔\mathrm{NewCanvas}\left(\left[''Write\; some\; expressions\; anywhere,\; then\; press\; the\; button\; to\; \text{'}complexify\text{'}\; your\; input\; into\; something\; equivalent\; but\; more\; complicated!''\,\mathrm{ScriptButton}\left(''Complexify''\,\mathrm{Complexify}\right)\right]\right)\:$

$\mathrm{ShareCanvas}\left(\mathrm{cv}\right)$

The DocumentTools[Canvas][Script][ToString] command was introduced in Maple 2021.

For more information on Maple 2021 changes, see Updates in Maple 2021.