I found this so helpful! If you have trouble switching audio interfaces or opening ProTools when an old session had different Playback engine settings… you can just hold the ‘N‘ key to bring up the Playback Engine while ProTools is starting up.
Who would have known?
Hear Spot Bark, Jason Tuttle. Awesome. http://hearspotbark.com/blog/2014/3/15/protools-tip