Disable a string is not possible

[kasoft]

The Docs say: Each header has a reference link in config file, you should read it if you do not know the header. If you want to disable a string type header, just set to null or empty string.

for example "prefetch-src" is experimental. You cannot remove it, just leave it empty. So this will throw a Browser notice. It would be better to remove it.

Content Security Policy: Unbekannte Direktive 'prefetch-src' kann nicht verarbeitet werden