How to disconnect a light path node My question seems obvious but I did not understand why I could not disconnect the path light node for other node. I have never had a problem with other node.
To disconnect any node ,I press the left button of the mouse on the output extremity of the link and I drag.  

Exemples:
That should work for any node.. But another way is to hold &#9096; Ctrl and drag  LMB, "cutting" the node link(s) (aka noodles):