boot like before, and make sure your external ssd is /dev/sda (it could change, run lsblk first, if it’s still /dev/sda then no need to change command below, if it was /dev/sdb or /dev/sdc, change the /dev/sda below to /dev/sdb or /dev/sdc).
mount /dev/sda2 /mnt
mount /dev/sda1 /mnt/efi
cp /mnt/efi/EFI/qubes/grubx64.efi /mnt/efi/EFI/boot/bootx64.efi
cp /mnt/efi/EFI/qubes/grub.cfg /mnt/efi/EFI/boot/bootx64.cfg
efibootmgr -v -c -u -L "TheEnemy1" -l /EFI/boot/bootx64.efi -d /dev/sda -p 1
reboot
boot into your uefi settings, change the uefi order, TheEnemy is your first order, TheEnemy1 is second.