System Configuration : I/O Setup : Session Interchange : Show Last Saved Setup and Show Current Setup

Show Last Saved Setup and Show Current Setup
When a session is opened that contains path definitions for unavailable I/O interfaces, the I/O Setup lists those paths in italics.
Clicking the Show Last Saved Setup button displays the audio interfaces used in the original session. This temporary display lets you check the last saved I/O configuration for reference while configuring the I/O settings for your system.
Once a session has been opened with unavailable I/O retained, you can then reassign tracks to available I/O paths.