Currently, if we have an .ics attachment with a single event in a Proton mail email, we are able to import that into Proton Calendar.
However, .ics attachments that contain multiple events are not yet supported, and show this message: "This ICS file contains more than one event. Please download it and import the events in Proton Calendar". This introduces a fair amount of friction.

I get these quite a lot as I often book train journeys where both the outbound and return journeys are sent to me as two calendar events within one ICS attachment.

Please change the Proton Mail ICS importer to add support for ICS files with multiple events. Thank you.