When building my workflow, let me hit a button disable automatic layout. In this mode, I can place my nodes wherever I want.
Hitting the Autolayout switch will instantly run a layout.
The Workflow Diagram probably needs to support undo/redo so that I can revert layout changes
This mode works really well with the idea of dragging the + button onto an empty patch of canvas and creating a node in that position (in the autolayout world, this interaction makes little sense)