Well you learn something new everyday. I thought they had removed that copy audio configuration entirely and there it is in the Mixer window. I can' try this out but can't you do this like before: copy configuration (I assume) in core, go to the enviroment, rubberband all tracks you want to switch, change them to direct TDM (if enabled), go back to the mixer/audio configuration and paste?
Otherwise the solution is to go back to Logic 7 and do this as described. best, jamie