I have absolute no idea if this works for efi installations,
but on my MBR based system, I have a stand alone grub partition
in /mainboot, and it has a simple grub.cfg file which gives
me menu items to boot one or the other fedora I have installed
via the configfile command. 

Oh, thanks...!

I also have a partition with /boot
I'm going to investigate a little what's there.
and then look at that little file you say: grub.cfg
Let's see what I find...
and I tell you... :-)

kind regards