Is it possible to delete calendar events to some kind of trash folder which allows me to restore event if I accidentally deleted it?
no this is not planned, but you can make another calendar name “trash” and you can move there events you don’t want to have in main calendar and after you are sure that you don’t need them just delete them or move them back.
This is workaround which I kept in mind as well.
But it is not always convenient:
Example 1. I want to delete event in advance which has notification set up. Delete event from “Trash” will emit notification.
Example 2. Deleting one event fro recurrent event series.
I understand that this is not best solution for you but we need to focus on more requested features.
but as usual if enough people will request this then we will consider it on idea meetings.