Thank you again for your kind response!
It might be that I'm worrying unnecessarily. I'm just not sure if the local storage cookies are flash-cookies which are used to identify users throughout sessions and browsers, hence my wish to be able to delete them simply.
The thing about your last point is that it doesn't work. If I open "all cookies and site data" and then "delete all" it shows me an empty list as if everything was deleted, if I reopen "all cookies and site data" afterwards the local storage cookies are still there. That's what I ment before