There's only so much customisation that you can get done with the
configuration options alone, as you have surmised, however this is
completely the wrong file to edit to achieve your goal.
The menus are created from templates kept in
/usr/share/live/build/bootloaders.
You are supposed to copy stu
My /auto/config has the line: "--bootloaders "syslinux, grub-efi". This
generates an image which can be installed both on bios and uefi machines
without any problem (i.e. grub-pc is installed for bios, and grub-efi-amd64 is
installed for uefi, both tested in virtualbox). For changing the grub me
