I'm sure parts of the PassEditor have been removed, but there must be enough parts left to use it at a basic level.
Oh, another thing; On the last two transition segments of Area1, rather than looping the transition over and over until I press the spacebar again, these two segments continue like any normal level segment. 9's transition segment does not loop objects however, but 10's does-I wonder if these where actually normal level segments at one point? And some of the Area5 transition segments last longer than they normally do, and are big enough to actually be normal level segments. But the objects don't loop however, so you end up floating in nothingness.
EDIT: Oh, and you can also load the final boss rush area from the level select by using the spacebar to select the next level, but the level entry model doesn't change until you select it-Area6 uses the Area5 entry model.