Open any report that does not have a list as output, for example, Open Incidents - Grouped.
For more information, see the product documentation topic Reporting.
This will create "Scheduled Execution of Open Incidents - Grouped." Available Type is "PDF-landscape" -default, PDF and PNG.
Go to Report > Scheduled reports.
"Scheduled Execution of Open Incidents - Grouped" is visible in list view.
Add the Type field to the list view.
The choices visible are "PDF-landscape" -default, PDF, Excel(.xlsx), Excel (.xls) and PNG, although Excel should not be included.
Instead of using the list view for modifying the export type, do so through the form itself.