Thanks, John. I have z in my list of modifiers.
While compiling my notes, I was thinking about compound notation for such
pieces as bent riders and Xiangqi horses. I have an idea involving () and
&, but wonder if other solutions exist.
Defining y as a modifier for 'away from the square of origin' (a common
enough limitation in these moves), we might have:
(W&yF) for the Xiangqi horse
F(F&yR) for the Gryphon.
I also considered extended notation for leaps greater than (3,3). Since
there is an indefinite number of such leaps, the possibility of something
like [14] comes to mind in lieu of another hard-to-remember letter for a
(1,4) leaper.
[17][55] for the Root-Fifty Leaper.
I don't know what other extensions may be in existence or proposed.