The multiselect.clear() method clears the current multi-selection.
DayPilot.Month.multiselect.clear(dontRedraw)dontRedraw (boolean) - set to true if the event calendar should not be automatically updated using DayPilot.Month.multiselect.redraw()
dpm.multiselect.clear();DayPilot.Month.multiselect.redraw()
Event Selecting [doc.daypilot.org]