The efibootmgr(8) is lacking proper documentation of the options -d (assuming device?) and -p (assuming partition?), as those options appear out of the blue in the examples, explaining how to create variables: [...] The efibootmgr program can be used to create new EFI boot variables. To create a new boot var pointing to an installation on partition 1 of device ada0 using the given loader with a description FreeBSD-11: efibootmgr -c -d ada0 -p 1 -l/EFI/BOOT/BOOTX64.EFI -L FreeBSD-11 This will result in the next available [...]
-d -p aren't supported, so this should be easier to do. :) Also, the quoted text is no longer in the manual, so closing.