So the solution could be : 

- when creating a selection marker add ```selection-mark``` class to it 

- in ```drawer.js```

```
this.wrapper.addEventListener('dblclick', function(e) {
	if (my.interact || my.params.dragSelection) {
		// fire dblclick event only if "normal" marker
		if (e.target.tagName.toLowerCase() === 'handler' && !e.target.classList.contains('selection-mark'){
			// handle this event in wavesurfer.js -> createDrawer method
			my.fireEvent('mark-dblclick', e);
		}	
		else{
			my.fireEvent('clear-selection', e);
		}
	}
});
```

But, if I want to add a class to marker I can only do that in drawer.canvas.js (when marker is added to dom)... 

So the solution could be : 
- add a Marker option (dynamically) to set the type of marker when created
- when adding it to dom, adding a class to marker (or marker handler ?)
- check as above

What do you think ?