Arch linux not in boot menu

[Linux for blind general discussion]

I have 3 operating systems on the same disk. Windows, slint and, as of this morning, arch. Installed in just that order. The bios type is UEFI.
Slint runs grub, so I did not install it in arch.
After completing the arch install, I got back into slint and ran
update-grub
It found arch on /dev/sda7
When  I ran
efibootmgr
Arch was not listed there, however.
What step did I miss?