Custom connecting lines for custom rendered elements

Hi,
I want to draw connecting lines for custom rendered elements (the start and end event as getting rendered as a round rectangle now). I noticed that after custom rendering the elements, the connecting lines are still the same as before. So the diagram is not looking properly as below:

image

Any way to update the path of the lines?
Also, i wanted to draw custom line with a button (like circle shape) on top of it. Is that possible?

How did you customize bpmn-js? What type of connection is the custom connection supposed to be?