Diagram shapes get converted into SVG elements such as Path, Text, Image, or group (g) tags. These tags support the primary HTML event handlers (such as on click) and other attributes. It becomes essential to add a hiddle sibling with identification to work around this limitation.

var fooText = new KD.TextBlock({
    x: fooX,
    y: fooY,
    text: textFromDb,
    id: uniqueIdBasedOnDataFromDb, // This ID (or another property "domId") should become the Id in the HTML
    onclick: someMethod,
    customAttributeA: valueAFromDb,
    customAttributeB: valueBFromDb});

barGroup.append(fooText);