Is there a setting or something that ensures that all filenames within a vault a unique? I am trying to achieve that by consciously creating unique names ( ZK prefix), but is here a way to make Obsidian to keep track of the issue in case I mess up?
If you are putting all of your notes into one folder, then yes, Obsidian will enforce unique note titles because you can’t have files with the same name in a folder.
If you have notes in multiple folders, then Obsidian is not enforcing uniqueness. You could create a #feature-requests for this.