localstorage is legally the same as cookies

As also from your article

If in the site settings on your KEEP UNKNOWN COOKIES panel, a cookie that was not detected by the cookie-script scan is deleted from your script.

It should do the same thing for localstorage

Perhaps a specific option could be created

KEEP UNKNOWN LOCALSTORAGE/SESSIONSTORAGE

Unknown localstorage and sessionstorage is kept by default.