If I have tracks recorded and start to mix and automate and then decide to add another track,can I deactivate the automation to free up the mix or do I have to live with The automated tracks and levels I already have?
1. Set the automation mode on the track to Off. That way the automation is still there if or when you want it. The Off mode acts as kind of like a "bypass" button.
2. Delete the automation on the track. You can get to this from under the Track menu.
3. If you do decide to keep and use the automation, you can easily scale it to fit the revamped arrangements by command dragging the yellow bar in the track header that is visible when you are expanded and in automation view.
4. You could use a gain plug-in on your channel strip to scale the already existing automation as necessary.
Anyway - just some idea to get you going. there are certainly other ways of handling the situation as well....