this.schedulerProComponent.instance.project.calendar contains an id or model of currently active calendar.
See docs https://bryntum.com/docs/scheduler-pro/api/SchedulerPro/model/ProjectModel#config-calendar
To set a list of calendars please use
For initial data:
https://bryntum.com/docs/scheduler-pro/api/SchedulerPro/model/ProjectModel#config-calendarsData
For loading data at runtime we have https://bryntum.com/docs/scheduler-pro/api/SchedulerPro/data/CalendarManagerStore
Try to set data with
this.schedulerProComponent.instance.calendarManagerStore.data = calendars;
And after that set active calendar using your code
this.schedulerProComponent.instance.project.calendar = calendarId;
