Yep, I meant the .obsidian folder (this hyphen-thing is usual in german…)
I used this macOS Service for creating the symlink easily: GitHub - nickzman/symboliclinker: A contextual menu plugin & service for Mac OS X that allows users to make symbolic links in the Finder
So in my vault, the .obsidian folder is a symlink pointing to another folder on my iCloud drive containing all necessary data for obsidian. Since Obsidian Sync does not sync the .obsidan folder but all other files in my vault, there is no trouble.
I hope this helps.