Dear Aditya and Fabrice,
thanks for your responses.

I included some of Fabrice's code into mine for testing purpose, and indeed the multipage works now.
What is bizarre is that issues appear now that didn't appear before:
Adjusted mwe:

\enableregime[utf] % enable unicoded input

\definefontfamily [RomanFont] [rm] [calluna]

\definefontfamily [KoreanFont] [rm] [applemyungjo]

\definefontfamily [JapaneseFont] [rm] [hannotatesc]

\definefontfeature
 [fea]
 [mode=node,language=dflt,script=arab,
  init=yes,
  medi=yes,
  fina=yes,
  isol=yes,
  calt=yes,
  rlig=yes,
  tlig=yes,
  trep=yes,
  curs=yes,
  kern=yes,
  mark=yes
]

\starttypescript [serif] [notonaskharabic]
 \definefontsynonym [notonaskharabic-Light]       [name:notonaskharabic]        [features=fea]
 \definefontsynonym [notonaskharabic-Bold]        [name:notonaskharabic]        [features=fea]
 \definefontsynonym [notonaskharabic-Italic]      [name:notonaskharabic]        [features=fea]
 \definefontsynonym [notonaskharabic-Bold-Italic] [name:notonaskharabic]        [features=fea]
\stoptypescript

\starttypescript [serif] [notonaskharabic]
 \usetypescript[serif][fallback]
 \definefontsynonym [Serif]                       [notonaskharabic-Light]       [features=fea]
 \definefontsynonym [SerifItalic]                 [notonaskharabic-Italic]      [features=fea]
 \definefontsynonym [SerifBold]                   [notonaskharabic-Bold]        [features=fea]
 \definefontsynonym [SerifBoldItalic]             [notonaskharabic-Bold-Italic] [features=fea]
\stoptypescript

\starttypescript [notonaskharabic]
  \definetypeface [notonaskharabic] [rm] [serif] [notonaskharabic] [default]
\stoptypescript

\usetypescript[notonaskharabic]

\setupbodyfont [RomanFont]
   
\usecolors[crayola]

\startMPinclusions

picture p[];
 path TheFrame ;
 TheFrame := fullsquare scaled 5in ;

 z0 = (0,0);   
 z1 = (60,40);
 z2 = (40,90); 
 z3 = (10,70);
 z4 = (30,50);
 z5 = (90,70);
 z6 = (-10,70);

path A; A = z0..z1..z2..z3..z4 ;
pair AStartPoint; AStartPoint = point 0 of A;
pair AEndPoint; AEndPoint = point 4 of A;
path B; B =  z5..z6;
pair BStartPoint; BStartPoint = point 0 of B;
pair BEndPoint; BEndPoint = point 1 of B;
path C; C = AStartPoint..AEndPoint;

p1:=image(
    draw A withcolor red;
);

p2:=image(draw A; label(lmt_outline [
text = "\JapaneseFont 日本語"
    ], AEndPoint););

p3:=image(
    label(textext("\notonaskharabic \textdir TRT دانگ") scaled 1.2, BStartPoint);
);

p4:=image(draw A; label(lmt_outline [
text = "\KoreanFont 한국어"
    ], AStartPoint););

p5:=image(
    label(textext("bāng"), BEndPoint);
    draw C withcolor green;
);

p6:=image(
    draw B withcolor blue;
);
\stopMPinclusions

\starttext

\dorecurse{6}{ % Frame
 \setupMPpage[background=color, backgroundcolor=SpringGreen]
\startMPpage[pagestate=start]  
 currentime := #1 ;
 % Just for learning :
 draw TheFrame withpen pencircle scaled .1in withcolor magenta ;
 draw textext("T="&decimal(currentime)) scaled 2 shifted(0,2in) withcolor magenta ;
 for k=1 upto currentime: draw p[k]; endfor
 setbounds currentpicture to TheFrame ;

 desiredformat := 1080;% In pixels (will be converted by default at 72dpi)
 currentpicture := currentpicture xysized (desiredformat ,desiredformat );
 
\stopMPpage
}

\stoptext
On Nov. 27 2023, at 11:25 pm, Aditya Mahajan <adityam@umich.edu> wrote:
On Mon, 27 Nov 2023, Fabrice L wrote:

> Hi,
>
> It is fun fact very easy to do. You just use \startMPpage (…) \stopMPpage multiple times. Here is an example which build an animation of a particle moving according to a Brownian motion.

A very similar option is to pass a variable to a metapost drawing. This is what I use:

https://adityam.github.io/context-blog/post/metapost-animation/

It only works when viewed in acrobat, you can just comment out the animation part and wrap it in \startTEXpage .. \stopTEXpage to get multi-page animation.

Aditya___________________________________________________________________________________
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