Yes, it is possible to export multiple Outlook calendars into a single ICS file, but Outlook itself doesn’t provide a direct option to merge multiple calendars into one ICS. Usually, users have to export each calendar separately and then combine them manually, which can be time-consuming. In such cases, tools like SysInfo PST Converter Tool simplify the process by allowing you to select multiple calendar folders from a PST file and export them together into a single ICS file while maintaining the original data structure.
Read more: https://www.sysinfotools.com/blog/export-outlook-calendar-to-ics/