@j-ed Ah, that worked indeed, I just pushed the red refresh button in the bottom-right corner.
Great, works for nextcloud, assuming that if I change the name of a shared calendar there, it doesn’t change it system wide. Zimbra doesn’t allow renaming of the base calendar it seems though (known “bug” on their side since almost a decade: https://bugzilla.zimbra.com/show_bug.cgi?id=31872).