I just wanted to know, if there's any way to delete the dialog notes in the Daggerfall Logbook, that are inscribed using the "copy to log"-button.

Nope. Not in game, at least. It may create a "logbook" file or something in your save directory, which you could probably just delete.

If it does, it's pretty well hidden. Couldn't find a file, which contains the log.
Thanks nevertheless.