Define a Grafana endpoint
Create a report schedule using a Grafana report template
Change the Grafana dashboard to something other than the first dashboard in the pulldown (note they are in alphabetical order)
Enter whatever other required information.
Check "Schedule this report", define a schedule, and click "Schedule Report"
Under the Report Schedules tab, edit the report schedule.
Notice the Grafana dashboard has been reset to the first dashboard in the alphabetical list.
I would expect the dashboard to stay the same so that editing my schedule doesn't inadvertently reset the dashboard I'm using for the report.