A quoted string that is the HTML
id of the target canvas element. This creates a timeline in canvas element with the ID "myTimeline".
Thus it targets:
<canvas id=""myTimeline" width="850" height="600">
As the value of element is an HTML ID ensure the name chosen is a valid HTML ID string (A-Z, a-Z, 0-9, underscore, hypen; muse start with a letter; no accents, etc.).
The height and width of the canvas are set in HTML or via CSS - they are not Timeline JS parameters. However, the Timeline code export dialog does offer boxes allowing the user to preset height and width that are used by the exported code.