Re: how about a find-library-other-window command?

[Richard Stallman]

    C-x 4 or some such prefix could automatically add the command's context
    (buffer name + this-command) to the config variable, so the next call
    without C-x 4 will reuse this preference once explicitly defined by calling
    the command with the C-x 4 prefix.

That is not a good implementation, because it requires each command to
have special code to test the flag.  The original idea was both better
and simpler.

Another drawback of this method is you'd have to type C-x 4 C-x C-f.
That is a big drawback.

So this is ruled out.