Add an option to send an email after event has been ended

[Saxomania]

we are doing workshops and all event organization is done via Indico
we offer 2 workshops a month and user can choose an appointment and self register

we automated reminders via email (to remind that workshop will start in day and 2 hours) but we want to send also an automated email AFTER workshop ended to all participants with the presentation file and some more information

but there is no reminder or something to do it

Alternatives:

I set a "reminder" to a fixed date but this not relative to the appointment and has to be changed for every single appointment

I do it manually via actions menu afterwards but thats like a nineties behaviour

Did I miss some other opportunity?