Three-pane editor: searchable grouped symbol stencil with drag-drop, typed/grouped property panel (string/int/float/enum/color/catalogue/list editors), toolbar (file, undo/redo, edit, zoom, run-flow), settings dialog (grid, snap, jumpover, color scheme, theme) and flow legend. Wires global keyboard shortcuts and seeds a demo network. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>