Would you consider using a report source with the required filters you want to include to help people filter out content?
The report would provide more filtering options in comparison to the calendar.
So instead of the 'Calendar' there is a dedicated report that lists upcoming seminars and allows the user to use any combination of configured filters to search for and navigate to the desired course?
I think there is a feature request for the Catalogue here: Add seminar dates as a filter option in the catalogue.