At the moment you can use a local menu set "My" with a local interface.pl
This is update save
But I can add the encoding as an editable parameter to the menu control file about-menus.txt
You can then modify this for a local menu set (ex My, update save)
http://napp-it.org/doc/downloads/advanced_user.pdf
I cannot use this as default as this would break file listings ex with german umlauts.