[req.] Add to User-Settings: `[ ]` Debug `"payload"` only

I created the concept of "alias nodes" as a method of setting alternative default values but that got no traction. That's a editor-only solution to having nodes with different default values. It's a non-standard and liable to break solution but it does the job now for v4.x (and 3.x also).

A debug node that uses complete message as default is included in this flow.