Thanks everybody. I think frankandfree has pointed me in the right direction. Just out of curiosity though, I've tried pressing "O" and ALL of the tracks suddenly jump to Unity - armed or not. That's not actually what I'm talking about. In the method that I'm hoping to be able to use at will, I press "W" on a track and ONLY that fader jumps up to Unity. Everything else stays where it was - unless it's armed to write also.  The selected track shows the progress of the automation when armed, but when I come out of "W" the fader is stationary and I'm able to move it to control the volume of the entire automated program. I get this in some projects and not others and I'm trying to understand how to control the choice - it can be very useful. Thanks again.
Sorry for the confusing description, it's difficult to articulate.
 
Best,
 
Nick
 

The reason that the faders all jump to unity when pressing O is because you have entered offset mode and unless you change a fader in that mode you haven't actually offset anything yet.

If you are sure offset mode is not causing the problem I would leave well alone for now. Offset mode is there to allow you to make overall adjustments of a track without affecting existing automation. i.e. If you lower a volume fader by -3dB in offset mode you are effectively lowering every node on that tracks volume envelope by 3dB even though that isn't reflected in envelope mode. More confusingly, perhaps is that changes made in offset mode aren't reflected in envelope mode either.

I'm a little confused as to what you are seeing exactly. Any chance you can do a screen capture so we can see a video?

Yes, it would make sense (to me anyway) if, after adjusting something whilst in Offset mode, the envelope would snap to its new position once you go back to Envelope mode, otherwise things could get (for me) horribly messy.