Amplitude Fader Button GONE among other things.....

1) Edit>Preferences>Display and at the bottom of the pane there's an option to have the on-clip gain control visible all the time.

2) You can't disable the mixdown option, but the way around your problem is to use File>Export. On the export setup screen you get to name the file (which is generally rather more use than the auto-name that a mixdown does anyway...), and select exactly what it does when it's been saved. Export has way more options than doing a mixdown - once you've realised this you'll probably never want to use anything else!

3) In your sound device hardware setup, there's an option that says 'release ASIO driver in background', and that's almost certainly got a check in it. This means that if you minimise Audition, the audio driver gets released... and that's exactly what you don't want it do do. Taking the check out will enable Audition to continue to play whenever the screen focus is shifted.

Pressing 6 on the main keyboard (not the numerical one) should toggle it on and off. It's also in the View menu as On Clip UI.

Thank you so much for this answer.  In edit mode my gain and my fade out squares disappeared and they are such handy tools.  Pressing 6 brought both back.   Thank you again.