Calendar: clicking top-right corner of an event hides it, even though there is no X there
Unlike notifications for calendar events on the current day, notifications for future & past calendar events do not have a close icon "X" in their top-right corner. Despite this, clicking the top-right corner of a future or past event notification still hides it from the calendar.
In this picture, clicking the mouse at the shown cursor location will hide the event. Because of that, a close icon should be there. Otherwise, clicking there shouldn't hide the event.
This wouldn't be so bad if it were easy to re-display calendar events that are hidden this way, but as far as I'm aware, the only way to do that is to delete ~/.local/share/gnome-shell/ignored_events and restart the shell.
Edited by Xavier Johnson