man less tells us the following:
You may define your own less commands by using the program lesskey
(1) to create a lesskey file. This file specifies a set of command
keys and an action associated with each key. You may also use
lesskey to change the line-editing keys (see LINE EDITING), and to
set environment variables. If the environment variable LESSKEY is
set, less uses that as the name of the lesskey file. Otherwise,
less looks in a standard place for the lesskey file: On Unix
systems, less looks for a lesskey file called "$HOME/.less".
It tells us to use
lesskey to generate a lesskey file reading
man lesskey fills in the details. You can put the following in the lesskey input file (
~/.lesskey by default)
lesskey, and it will generate an output file (
~/.less by default) for you.
As far as I can tell, you can't do character-by character horizontal scrolling.