Not sure about this question 'yamaha wrote'
But as far as saving favs.....Yes .....you can copy styles to user from all psr s /tyros and genos models from USB to your user drive on the 900.well as far as I am aware
I have over 10,000 in user, handy to search from if you 'song title' them ...and they dont take up a huge space.
Some I have found will save to favourite, where others wont ...another member might be able to specify why.
Before the last firmware update version ( you last question on the forum....I note no reply ) it only seemed possible to save 'preset' styles and voices to favourite. but now I have noticed other styles, well some can be saved....Note... there is a limit to 100 styles available to store in favs.
Hope that helps
Keith
ps...another solution is to create your own fav. folder in user then there is no limit to how many you keep in it, or no issues if some of your fav.styles are not saveable in the regular fav. way.