Customize in what way? Perhaps you have an example.
The only way this could be achieved, would be to expose all built-in click functions, so they can be customized via custom Javascript. For example the below. It's not currently possible, but I might consider it, although it's quite a big task to implement properly.
actions: {
get_copy_link: function(item){
// item is an object containing all properties of the clicked item. You would have to create your own function that returns a link.
return 'something.php?' + item.path;
}
}
Another option would be to allow custom links in the context menu, but that would require the same approach as above, and more properties to assign icons and text to the custom link.
For now, sorry no.