How may I change the default boot image?

I have installed 4.4.194-19-rockchip-g287ff75afc47.
/boot/extlinux/extlinux.conf shows the relevant entry.
How do I tell the system to boot to this image?

I have solved another problem with a kludge as shown here,

I would like to try to solve the issue properly, but the penultimate comment suggested a more recent kernel.

With my present predicament, this solution will not work until someone helps me make my Rock Pi boot to a newer kernel.

I warmly welcome any assistance.

Sincerely,
oliphant