EFI amd64: boot.cfg goes where?

I'm running an EFI-booting amd64 NetBSD 10.1 system with the
following uname -a:
>NetBSD toughbook.lan 10.1 NetBSD 10.1 (GENERIC) #0:
>Mon Dec 16 13:08:11 UTC 2024
>[email protected]:/usr/src/sys/arch/amd64/compile/GENERIC amd64

I'm using rEFInd to boot either MS Windows, GNU+Linux, or NetBSD, and
each live in the ESP under the respective folders windows/, ubuntu/,
netbsd/. I copied the NetBSD EFI loader from /usr/mdec/bootx64.efi to
netbsd/ and rEFInd sees it, so I can get into the boot prompt and run
>root NAME=3DNETBSD
>boot NAME=3DNETBSD:netbsd
and the system booted and I'm happily using it now. I've put these lines
into a file named boot.cfg but now I'm a bit lost as to where exactly to
put it in order to get the EFI loader to see it.

My ESP is mounted at /boot/efi, so I've tried placing boot.cfg in the
root of that file system and in its subdirectories EFI/ and EFI/NetBSD/,
and the booter hasn't seen any of these. I saw mention of someone
putting their boot.cfg in their system root but that didn't work for me.

Currently by default the EFI loader tries booting various kernel names
in NAME=3DESP and gives up. I haven't tried copying over the kernel to the
ESP.

Thanks for any help.
:3 <3 -3