How to persist or append kernel parameters in u-boot configuration file /boot/extlinux/extlinux.conf?

[Jibun-no-Kage]

How to persist or append kernel parameters in u-boot configuration file /boot/extlinux/extlinux.conf? Say I need to add 'ipv6.disable=1 to the append command for the given profile in the extlinux.conf file. If I edit the file, the changes are lost whenever some update or package invokes u-boot-update. How can I stop this behavior?

I tried adding the additional parameters to the /etc/default/u-boot file, per the u-boot documentation but this file seems to be completely ignored by u-boot-update? I added...

U_BOOT_PARAMETERS="ipv6.disable=1 fsck.mode=force fsck.repair=yes"
U_BOOT_TIMEOUT="60"
U_BOOT_FDT_OVERLAYS="/boot/gpiod-line-names.dtbo"

None of the above was in the /boot/extlinux/extlinux.conf file after u-boot-update was executed.