(address . bug-guix@gnu.org)
To dual boot with NixOS and other operating systems it would be nice to have 'chainloader' so that this configuration would work:
(bootloader
(bootloader-configuration
(bootloader grub-efi-bootloader)
(target "/boot/efi")
(menu-entries
(menu-entry
(label "systemd-boot")
(chainloader "/EFI/Boot/bootx64.efi")))