Sometimes a missing feature results from the specifics of your project.  For example, features related to MIDI might be missing if you (a) don't have any midi devices selected in preferences or (b) if your project only has audio tracks. Example 1:  Problem: Instrument Definitions are not showing up where they used to!!! PROBLEM:    WHY?  No MIDI Devices checked!!! Example 2: Problem: On the Menu Bar under Views, PRV [Piano Roll View] is grayed out and cannot be selected!!! PR