Sorry, Plan 9 does not use cursor keys in editing, not even for
left/right.  This is a design decision.  Plan 9 use the mouse as it's
main form of interaction.  The keyboard, you might say, is an
necessary evil for the entry of characters, but not much else.
Everything in acme is done using the mouse apart for text entry (and
acme does everything).

To recap the logic (it has been repeated many times in the archives),
once you switch to mouse centric operation, you become faster, not
slower.  It may be counterintuitive, but I believe it has been shown
by research, not that I can quote anything.  You have to move your
hands to get to the cursor keys, so it's a whole bunch better if your
default position is holding the mouse as it does lots of things
besides positioning the cursor.

We've all been keyboard centric at one time in our lives, and I think
I speak for the vast majority of the list when I say that we don't
miss cursor keys.  At all.  In fact, quite a few people buy keyboards
without cursor keys, function keys, windows keys, number pads and
reclaim a good square foot of their desk.

So, stick with it, persevere, and you'll hopefully feel the benefit.

Nigel