For what it’s worth since there is no what’s new guide as of yet nor a Cubase 9 manual here is a side-by-side of Cubase 8.5 preferences versus Cubase 9 preferences. I didn’t go through all the drop down menus. Note that several things just were shifted to other locations, stationay cursor has moved its way out of the preferences all these years to being under the edit commands now though oddly it is not under the edit menu in Cubase (only in key commands).