Given all the discussion and requests for a way to segue from song to song, I bet the good folks at Abelton are probably working on this as the next enhancement--a better way to compile or import projects into a larger one. For me, just being able to pre-listen to a full project before opening/importing it would be great.
Something along these lines would be a lifesaver for putting together potential setlists from existing projects. By "setlist" I don't mean laying out the order, but choosing a group of songs tracks that could be used in a set. Some tracks I've saved have some interesting potential but are nowhere near where I'd want to play them out, while others are the wrong style for a particular gig, so I don't want to be sifting through those no-go's in front of 600 people during the 5 minutes I have when tag-teaming with a DJ.
I use the Arranger for some tunes and the session for others, and it is pretty labor intensive to compile all these songs into one session, and they quickly get unwieldy to navigate once you get more than about 15 songs loaded end to end in the arranger view