A 'Start-up' bank - usually with just one registration, is something that I've been getting my students to do for almost 20 years!
It usually gets called A BLANK, as in 'a blank sheet of paper', which means it's easy to find! You should find that it will evolve over time, as you find your way around the new keyboard and start to get a bit more fussy about your settings. ALWAYS use it when starting a new registration bank (unless you're making a close copy of an existing one) and ALWAYS back it up as something like Z BLANK, for that O M G! moment when you realise you've just accidentally saved your newly created bank of sounds as.... A BLANK!
And it's the perfect antidote to 3rd part registrations, or OTS, Playlist registrations or (on older keyboards) Music Finder, which, as has already been said, will happily mess up your carefully set up split points etc etc.
I would love to have the ability to then save this as a default start-up setting on power-up and indeed have argued this up at Yamaha HQ, but the fact remains that it's just two or three button pushes and a few seconds of time to do it the way we have to, so who's really worried!