That is currently a read-only page, so you can't remove cookies or edit items in other storage types.

• https://developer.mozilla.org/en-US/docs/Tools/Storage_Inspector

Note that you can also use the 'cookie list' command in the Developer toolbar to inspect cookies

• • https://developer.mozilla.org/Tools/GCLI

The cookie list command has never worked for me. Always says there are no cookies for the current domain despite the Storage (and 3rd party cookie managers) showing them. And anyway, its not nearly as clean as just deleting them from Storage like the other browsers support.