diff --git a/client/src/canvas/draw_legend.ts b/client/src/canvas/draw_legend.ts
index 944886c..c830683 100644
--- a/client/src/canvas/draw_legend.ts
+++ b/client/src/canvas/draw_legend.ts
@@ -55,98 +55,100 @@ function drawRoundedRect(
 
 // set the canvas properties
 const canvas = document.getElementById('myCanvas') as HTMLCanvasElement;
-const width = window.innerWidth;
-canvas.width = width;
-const scalingFactor = width / 400; // adjust the legend size according to the screen width
-canvas.height = 460 * scalingFactor;
-const ctx: CanvasRenderingContext2D = canvas.getContext('2d');
+if (canvas != null) {
+  const width = window.innerWidth;
+  canvas.width = width;
+  const scalingFactor = width / 400; // adjust the legend size according to the screen width
+  canvas.height = 460 * scalingFactor;
+  const ctx: CanvasRenderingContext2D = canvas.getContext('2d');
 
-// style properties for the legend that are found to fit well
-//// circles
-const circleRadius = 15 * scalingFactor;
-const circleX = 30 * scalingFactor;
-const orderedCircleColorsAndLabels = [
-  ['--component-started-color', 'Component started'],
-  ['--component-finished-color', 'Component finished'],
-  ['--component-done-color', 'Component done'],
-  ['--statement-passed-color', 'Statement passed'],
-  ['--statement-failed-color', 'Statement failed'],
-  ['--statement-entry-color', 'Loop / Condition entry']
-];
-//// boxes
-const rectX = 17 * scalingFactor;
-const rectWidth = 27 * scalingFactor;
-const rectBorderRadius = 6 * scalingFactor;
-const orderedBoxColorsAndLabels = [
-  ['--task-box-color', 'Task'],
-  ['--service-box-color', 'Service'],
-  ['--condition-box-color', 'Condition'],
-  ['--loop-box-color', 'Loop'],
-  ['--parallel-box-color', 'Parallel']
-];
-//// descriptionText
-const textX = 80 * scalingFactor;
-//// entries
-const lineWidth = 2 * scalingFactor;
-const lineHeight = 40 * scalingFactor;
-const objectsHeightDifferenceCircleAndBox = -10 * scalingFactor; // the boxes are bigger, so make the gap between the circle and box smaller
-let objectsLineStartY = 30 * scalingFactor;
-const fontSize = 27 * scalingFactor;
-const textHeightDifferenceCircleAndBox = 4 * scalingFactor; // same as for the objects
-let textLineStartY = 39 * scalingFactor;
+  // style properties for the legend that are found to fit well
+  //// circles
+  const circleRadius = 15 * scalingFactor;
+  const circleX = 30 * scalingFactor;
+  const orderedCircleColorsAndLabels = [
+    ['--component-started-color', 'Component started'],
+    ['--component-finished-color', 'Component finished'],
+    ['--component-done-color', 'Component done'],
+    ['--statement-passed-color', 'Statement passed'],
+    ['--statement-failed-color', 'Statement failed'],
+    ['--statement-entry-color', 'Loop / Condition entry']
+  ];
+  //// boxes
+  const rectX = 17 * scalingFactor;
+  const rectWidth = 27 * scalingFactor;
+  const rectBorderRadius = 6 * scalingFactor;
+  const orderedBoxColorsAndLabels = [
+    ['--task-box-color', 'Task'],
+    ['--service-box-color', 'Service'],
+    ['--condition-box-color', 'Condition'],
+    ['--loop-box-color', 'Loop'],
+    ['--parallel-box-color', 'Parallel']
+  ];
+  //// descriptionText
+  const textX = 80 * scalingFactor;
+  //// entries
+  const lineWidth = 2 * scalingFactor;
+  const lineHeight = 40 * scalingFactor;
+  const objectsHeightDifferenceCircleAndBox = -10 * scalingFactor; // the boxes are bigger, so make the gap between the circle and box smaller
+  let objectsLineStartY = 30 * scalingFactor;
+  const fontSize = 27 * scalingFactor;
+  const textHeightDifferenceCircleAndBox = 4 * scalingFactor; // same as for the objects
+  let textLineStartY = 39 * scalingFactor;
 
-// draw the legend symbols as coloured circles and rectangles
+  // draw the legend symbols as coloured circles and rectangles
 
-// draw the circles
-for (const [circleColor, circleLabel] of orderedCircleColorsAndLabels) {
-  // draw the colored circle
-  ctx.beginPath();
-  ctx.arc(circleX, objectsLineStartY, circleRadius, 0, 2 * Math.PI);
-  ctx.fillStyle = getComputedStyle(document.documentElement).getPropertyValue(
-    circleColor
-  );
-  ctx.fill();
-  ctx.lineWidth = lineWidth;
-  ctx.stroke();
+  // draw the circles
+  for (const [circleColor, circleLabel] of orderedCircleColorsAndLabels) {
+    // draw the colored circle
+    ctx.beginPath();
+    ctx.arc(circleX, objectsLineStartY, circleRadius, 0, 2 * Math.PI);
+    ctx.fillStyle = getComputedStyle(document.documentElement).getPropertyValue(
+      circleColor
+    );
+    ctx.fill();
+    ctx.lineWidth = lineWidth;
+    ctx.stroke();
 
-  // draw the label
-  ctx.font = String(fontSize) + 'px arial';
-  ctx.fillStyle = '#000000';
-  ctx.fillText(circleLabel, textX, textLineStartY);
+    // draw the label
+    ctx.font = String(fontSize) + 'px arial';
+    ctx.fillStyle = '#000000';
+    ctx.fillText(circleLabel, textX, textLineStartY);
 
-  // set the start height for the next line
-  objectsLineStartY += lineHeight;
-  textLineStartY += lineHeight;
-}
+    // set the start height for the next line
+    objectsLineStartY += lineHeight;
+    textLineStartY += lineHeight;
+  }
 
-// adjust the start height for the next line when switching from circle to box
-objectsLineStartY += objectsHeightDifferenceCircleAndBox;
-textLineStartY += textHeightDifferenceCircleAndBox;
+  // adjust the start height for the next line when switching from circle to box
+  objectsLineStartY += objectsHeightDifferenceCircleAndBox;
+  textLineStartY += textHeightDifferenceCircleAndBox;
 
-// draw the boxes
-for (const [boxColor, boxLabel] of orderedBoxColorsAndLabels) {
-  ctx.beginPath();
-  drawRoundedRect(
-    ctx,
-    rectX,
-    objectsLineStartY,
-    rectWidth,
-    rectWidth,
-    rectBorderRadius
-  );
-  ctx.fillStyle = getComputedStyle(document.documentElement).getPropertyValue(
-    boxColor
-  );
-  ctx.fill();
-  ctx.lineWidth = lineWidth;
-  ctx.stroke();
+  // draw the boxes
+  for (const [boxColor, boxLabel] of orderedBoxColorsAndLabels) {
+    ctx.beginPath();
+    drawRoundedRect(
+      ctx,
+      rectX,
+      objectsLineStartY,
+      rectWidth,
+      rectWidth,
+      rectBorderRadius
+    );
+    ctx.fillStyle = getComputedStyle(document.documentElement).getPropertyValue(
+      boxColor
+    );
+    ctx.fill();
+    ctx.lineWidth = lineWidth;
+    ctx.stroke();
 
-  // draw the label
-  ctx.font = String(fontSize) + 'px arial';
-  ctx.fillStyle = '#000000';
-  ctx.fillText(boxLabel, textX, textLineStartY);
+    // draw the label
+    ctx.font = String(fontSize) + 'px arial';
+    ctx.fillStyle = '#000000';
+    ctx.fillText(boxLabel, textX, textLineStartY);
 
-  // set the start height for the next line
-  objectsLineStartY += lineHeight;
-  textLineStartY += lineHeight;
+    // set the start height for the next line
+    objectsLineStartY += lineHeight;
+    textLineStartY += lineHeight;
+  }
 }
diff --git a/client/src/code_visualization/element_creation.ts b/client/src/code_visualization/element_creation.ts
index c20dfcb..c79b808 100644
--- a/client/src/code_visualization/element_creation.ts
+++ b/client/src/code_visualization/element_creation.ts
@@ -11,7 +11,7 @@ import { Point } from '../types/point';
  * read out the stored HTML data to create nodes, edges and containers to visualize the PFDL program.
  * @returns graph elements as valid JSON strings that are accepted by cytoscape
  */
-export function getGraphElements() {
+export function getGraphElements(parsedDotfile = null) {
   // retrieve graph data
   const dotfileContent = document.getElementById('graphElementsDiv').innerText;
   if (dotfileContent == null || dotfileContent.search('graph') == -1) {
@@ -23,12 +23,15 @@ export function getGraphElements() {
 
   const containers = buildTreeStructure(treeStructure, dotfileString);
 
-  // 3rd party package
-  const parse = require('dotparser');
-  const parsedContent = parse(dotfileString)[0];
+  if (parsedDotfile == null) {
+    // parse the dotfile here
+    // 3rd party package
+    const parse = require('dotparser');
+    parsedDotfile = parse(dotfileString)[0];
+  }
 
   // convert into utf-8 string
-  const [nodes, edges] = parseElementsFromDotFileString(parsedContent);
+  const [nodes, edges] = parseElementsFromDotFileString(parsedDotfile);
   return getFinalGraphElements(nodes, edges, containers);
 }
 
@@ -159,7 +162,7 @@ const loopTree = (
  * @param fileString a JSON string containing the graph objects
  * @returns an array containing all existing nodes and edges in the dotfile
  */
-const parseElementsFromDotFileString = (
+export const parseElementsFromDotFileString = (
   fileString: any,
   standaloneTesting = false
 ) => {
diff --git a/client/src/code_visualization/graph_creation.ts b/client/src/code_visualization/graph_creation.ts
index ccb682e..54d151f 100644
--- a/client/src/code_visualization/graph_creation.ts
+++ b/client/src/code_visualization/graph_creation.ts
@@ -13,9 +13,9 @@ import { createTooltips } from './event_handler';
  */
 const getGraphElements = require('./element_creation').getGraphElements;
 
-export function createGraph(cy) {
+export function createGraph(cy, parsedDotfile = null) {
   // add all graph nodes to cytoscape
-  const elements = getGraphElements();
+  const elements = getGraphElements(parsedDotfile);
   if (elements == null) {
     return false;
   }
diff --git a/client/src/code_visualization/main.ts b/client/src/code_visualization/main.ts
index 2c1129f..e571bdb 100644
--- a/client/src/code_visualization/main.ts
+++ b/client/src/code_visualization/main.ts
@@ -6,32 +6,69 @@ import { setupCytoscapeInstance } from './setup_cytoscape';
 import { setupEventHandlers } from './event_handler';
 import { createGraph } from './graph_creation';
 import { rotateNodes } from './context_menu';
+import { parseElementsFromDotFileString } from './element_creation';
 
-const cy = setupCytoscapeInstance(document.getElementById('cy'));
-setupEventHandlers(cy);
+const cytoscapeDiv = document.getElementById('cy');
+if (cytoscapeDiv) {
+  const cy = setupCytoscapeInstance(document.getElementById('cy'));
+  setupEventHandlers(cy);
 
-// create the graph
-createGraph(cy);
+  // create the graph
+  createGraph(cy, null);
 
-// global function used to update the dashboard in the standalone browser version
-(window as any).createCodeVisualization = function (refreshData = true) {
-  if (refreshData) {
+  // global function to enable the dashboard in the standalone browser version to access the cytoscape instance
+  (window as any).getCy = function () {
+    return cy;
+  };
+
+  // global function used to update the dashboard in the standalone browser version
+  (window as any).createCodeVisualization = function (parsedDotfile = null) {
     cy.elements().remove();
-    const successfullyCreated = createGraph(cy);
-    if (!successfullyCreated) {
-      // no elements drawn
-      return;
+    createGraph(cy, parsedDotfile);
+    const imgElement = document.getElementById('codeVisuImg');
+    if (imgElement) {
+      // graph should be displayed as an image, rotate it
+      rotateNodes(cy.nodes(), cy.nodes('.container'), false);
     }
-  }
+  };
+
+  // global function for the dashboard in the standalone browser version to enable the comparison of two dotfiles
+  (window as any).getElementsFromDotfile = function (dotfile) {
+    return parseElementsFromDotFileString(dotfile);
+  };
 
-  // create and display image of the code visualization if the <img> element 'codeVisuImg' exists
-  const imgElement = document.getElementById('codeVisuImg');
-  if (imgElement) {
-    // only exists in standalone browser version (without vscode)
-    // create img of rotated graph
-    rotateNodes(cy.nodes(), cy.nodes('.container'), false);
-    const pngToDownload = cy.png({ full: true });
-    rotateNodes(cy.nodes(), cy.nodes('.container'), true);
-    imgElement.setAttribute('src', pngToDownload);
-  }
-};
+  (window as any).flipTokensForNodeIds = function (nodeIds) {
+    nodeIds.forEach((id) => {
+      const node = cy.getElementById(id);
+      const tokenNode = cy.getElementById(id + '_token');
+      if (tokenNode.length && tokenNode.inside()) {
+        // node had a token before, remove it
+        const newParentId = tokenNode.data('parent');
+        node.data('label', '');
+        node.move({ parent: newParentId });
+        node.classes(['single_node', 'upper_round_node']);
+        tokenNode.remove();
+      } else {
+        if (tokenNode.removed()) {
+          tokenNode.restore();
+        } else {
+          // create a new token node for the object
+          const newTokenNode = {
+            group: 'nodes',
+            classes: ['upper_round_node', 'token_label'],
+            data: {
+              id: id + '_token',
+              label: '',
+              tippyContent: node.label,
+              parent: node.parentId
+            }
+          };
+          cy.add(newTokenNode);
+        }
+        node.data('label', '•');
+        node.move({ parent: node.id + '_token' });
+        node.classes(['single_node', 'token_node']);
+      }
+    });
+  };
+}