Customize menu output in theme?

Hi,

I want to add my own custom content at the end of the menu (inside the offcanvas container, just after the menu). Is there a way to override the default template within a theme? I’ve tried copying offcanvas.php to my theme folder as /quadmenu/offcanvas.php, but it doesn’t seem to be working.

Any pointers for theme integration would be appreciated, thank you!