This interactive tree diagram visualizes a hierarchical scenario structure with collapsible nodes, showing steps and their sub-steps for a data flow. Built with D3 v7, it uses `d3.hierarchy` and `d3.tree` to compute layouts, while `d3.link` with `curveStepAfter` generates step-shaped paths between nodes. Users can click nodes to expand or collapse children, triggering animated transitions with `d3.transition`. The SVG rendering includes circles and text labels, with data imported from a JavaScript module. Collapsed nodes initially hide all descendants, revealing them progressively through click interactions.