Here an easiest solution for who wants to change the prorpio bootloader, Grub in this case, without to take part on the configuration rows. The utility QGRUBEditor is called and it can be unloaded on http://www.qt-apps.org/. This the link to the page. The installation is immediate, since it is possible to make the download of the paccheeti precompiled for the distro more diffuse, enough to make double click and to follow the video instructions.
Good smanettata…

It marks it near: