Dyson link should have the possibility to clear action

[pbrunier]

When you selected an action in the Dyson link node, it should be possible to clear the action. When the item is selected once, it is not possible to clear it.
This makes sending JSON with the action included useless, because the action is overruled by the action field. The possibility to clear the action prevents the need for the user to create a new node.

[pbrunier]

Isn't overruled as I thought. Won't fix.