menuentry "NetBSD" {
insmod part_gpt
insmod chain
chainloader (hd0,gpt2)/EFI/boot/bootx64.efi
}
I am not sure I followed everything, but if you've already gone that far and use GRUB instead, why not load the kernel directly from there?
menuentry "netbsd -v" {
insmod ufs2
set root=(hd0,gpt2)
knetbsd /netbsd -v
}
-elge