Connect an onclick event to the label. Function renderLabel. Add a line
this.connect(labelnode, 'onclick', dojo.hitch(this, this.nodeClick, labelnode, false));
Handle the click in the nodeClick function. If it is a url, connect the url to the label so you can use it. If it is a microflow call, invoke the it with execMF
the hardest part is to pass the label to the Microflow. The only way I know it to create an intermediate object, set the label value in an attribute, pass it to the Microflow and delete the object. You will have to make this entity a property of the widget, otherwise you can not call a microflow with that entity.