If your device is /dev/sda and efi partition is 1 then :
efibootmgr -v -c -u -L MichaelA -l /EFI/qubes/grubx64.efi -d /dev/sda -p 1
If you use qubes os as external device, folow this (I assume that your device is /dev/sda and efi partition is 1) :
cp /boot/efi/EFI/qubes/* /boot/efi/EFI/BOOT
mv /boot/efi/EFI/BOOT/grubx64.efi /boot/efi/EFI/BOOT/bootx64.efi
mv /boot/efi/EFI/BOOT/grub.cfg /boot/efi/EFI/BOOT/boox64.cfg
efibootmgr -v -c -u -L MichaelB -l /EFI/BOOT/bootx.64efi -d /dev/sda -p 1