Set enableRollups: true and each summary parent row gets thin markers below its summary bar at every
leaf descendant's date range. Each rollup picks up its child's colour, and milestones roll up as miniature
diamonds — so the parent row mirrors the underlying task shapes. Try collapsing a parent (click the chevron in the
task list) — the rollups stay visible so you can still see the underlying tasks at a glance.
Tip: collapse "Design" or "Build" to see how rollups preserve the children's positions and shapes.