not a scrollbar but you can use one of these approaches to navigate through your sketch.

You can either use zoom. or translate it by dragging the canvas arround.
Test it. use mousedrag to move it. or up and down to scale it.

1. int centerX = 0, centerY = 0, offsetX = 0, offsetY = 0;
   float zoom = 1.5;
   
   void setup() {
     size(800,600);
     centerX = 0;
     centerY = 0; 
     cursor(HAND);
     smooth();
   }
   
   void draw() {
     background(255);
     if (mousePressed == true) {
       centerX = mouseX-offsetX;
       centerY = mouseY-offsetY;
     }
   
     translate(centerX,centerY);
     scale(zoom);
   
     randomSeed(100);
     for (int i = 0; i < 100; i++) {
       float r  = random(100);
       fill(random(255),random(255),random(255));
       ellipse(random(width),random(height),r,r);
     }
   }
   
   void mousePressed(){
     offsetX = mouseX-centerX;
     offsetY = mouseY-centerY;
   }
   
   
   void keyPressed() {
     // zoom
     if (keyCode == UP) zoom += 0.05;
     if (keyCode == DOWN) zoom -= 0.05; 
   
   }
   
   
   

Thanks heaps :)

Hey this is nice, but what about 'text' data?
Like i have this list of 500 names which i am printing to the left side of the screen, and right now, its just fitting about 100 of them, and i want to display all with a scrollbar. How can i do that?