Which allows to use additional-options in menu-entry:
--8<---------------cut here---------------start------------->8---
(operating-system
…
 (bootloader
  (bootloader-configuration
   (bootloader grub-efi-bootloader)
   (target "/boot/efi")
   (menu-entries
    (list (menu-entry
           (label "Another distro")
           (linux "")
           (initrd "")
           (additional-options '("search --label --set another-disk-label"
                                 "configfile /boot/grub/grub.cfg")))))))
…)
--8<---------------cut here---------------end--------------->8---

Will produce the following Grub menuentry:
--8<---------------cut here---------------start------------->8---
menuentry "Another distro" {
  
  search --label --set another-disk-label
configfile /boot/grub/grub.cfg
}
--8<---------------cut here---------------end--------------->8---

I successfully reconfigured and dualbooted with attached patch.

Oleg.