Thanks for the info.
A bit sad because I have to admit that this magic little detail was always overwhelmingly encouraging for me in terms of user-friendliness. One click, and then another - my choice! - and then appeared not only an arbitrary overview (like the one in Raven or on Windows), but my own nextcloud synchronized calendar instead!
When it first happened I could barely believe it, and let me instantly fall in love with the OS and Budgie.