Rudder

Improvements have been done in #16993 but it is still quite difficult to drag and drop a method because of the size of the area, which is too small.
We should :
- Extend the size of the container to the bottom of the window to make it easier to add the first generic methods.
- Add an indication block at the beginning and the end of the list to make it easier to add methods at these places.
- And increase the trigger zone of the scroll in js