entering geli passphrase only once at FreeBSD boot

I am a Linux user and would like to set up a home server with ZFS for
backup. Although I could use Linux for that, I want to do it with
FreeBSD as I think it is easier to set up and maintain.

I already have the hardware, various old discarded bits including a
small hard disk of 250 GB and a bigger disk of 4 TB. The plan is to
have FreeBSD 13.0 on geli-encrypted ZFS in the small disk and the
backup in the big disk, also geli-encrypted. For now I am practising
with two virtual disks in VirtualBox.

I ran these commands for the backup disk:

geli init -s 4096 -l 256  /dev/ada1
geli attach  /dev/ada1
zpool create -o ashift=12 zbackup /dev/ada1.eli

This simple solution worked and I got my pool. The next step was to
make it work after reboot. After a number of tries I found a solution
that works:

# add to /etc/rc.conf
geli_devices="ada1"

The next goal was to find a way to enter the passphrase only once at
boot (to unlock zroot in ada0 and zbackup in ada1). After a number of
tries I found a solution that works:

# create file /pass-ada1 with passphrase
# add to /etc/rc.conf
geli_ada1_flags="-j /pass-ada1"

This sort of solution involving storing the passphrase in a file is
possible in Linux, however my preferred solution in Linux is not to
use such file (I use systemd-boot though perhaps there are other
ways).

Is there a way to enter the passphrase only once in FreeBSD that does
not involve storing it in a file?