The rows.expandAll() method expands all nodes of the resource tree displayed by the JavaScript Scheduler component.
DayPilot.Scheduler.rows.expandAll()
dp.rows.expandAll();
DayPilot.Scheduler.rows.collapseAll()
Resource Tree [doc.daypilot.org]
DayPilot.Scheduler Class
Availability of this API item in DayPilot editions: