I use the object handle at the end of each object. Of course, you'd have to do it to the object at the end of every track. If you have a lot of tracks, then you'll have a lot of objects to adjust.
I haven't been able to find anything descibing a way to fade out the entire arrangement at once.
Fading each track individually does allow you the flexibility to fade tracks out at different rates. For example, you could have the bass and drums fade out a little sooner or faster than the vocal track.
I wrote.... "I haven't been able to find anything descibing a way to fade out the entire arrangement at once."
One way this can be accomplished is to mix down your arrangement and export it as a WAV file. Then, you can import that WAV file into a new arrangement as a single object and use the end object handle to do a fade-out of the entire track. Export this as the final version.