> > Scroll lock key on keyboard switches from partial to full emulation which enables > and > > disables MAME's Internal UI > > Of all the keys on a modern keyboard, I can't think of any possible use for Scroll > Lock.
That's kind of the main reason why the MESS developers chose it as the toggle between keyboard modes: it was a key that wasn't already doing something (in the operating system or in MESS).
(We understand toggling between partial and full emulation modes might be a bit non-intuitive but there's not many other ways to do it...)