Allow draggable node even for an ultra lower values nodes.

[electroduende21]

When there is a lot of quantity value differences between 2 nodes, the draggable graphic shows an ultra thin node fo the lower value. This is a problem when you try to drag this node to re-locate, as it is sometimes impossible to catch it with the mouse.

Although the real graphic thickness of the flow is related to the node value, Could it be possible to have a draggable solution to handle this ?