Я попытался посмотреть, могу ли я добавить события в мою встроенную верхнюю панель calender.
Мне было предложено установить GNOME Calender, есть ли способ заменить собственный календарь Ubuntu на верхней панели новым календарем GNOME?
You don't need to replace anything with another thing. The top-bar calender in GNOME Shell is in sync with the pre-installed GNOME Calendar. If you and an event to GNOME Calender, it would also appear in the top-bar calender.
Right now there seems to be no other way to add events to the top-bar calender, so you have to add events to the GNOME Calendar application.