It's awesome to see that my first point was addressed, but I'm bumping this with a few more suggestions, although I hope the other two I mentioned in the first post aren't forgotten.
The first two are based on my experiences with 3DS Max. They're focused on speeding up and simplifying layout editing.
1) Object groups: Often I find myself creating slices of levels/puzzles as they come to me, and I later place them into the level as I see fit. This would be made 100 times easier if those objects could be grouped together and repositioned as a single object. This isn't an event/container thing, just a convenience thing in the layout view. I realise that box selection is the preferred method to deal with this, but it's not always suitable.
2) Lock/freeze individual objects: This would require a new object pane that would list all the locked objects, but it'd make it much easier when dealing with heavily layered layouts without having to lock entire layers.
Lastly, again this is a small niggle:
3) Comments above individual actions: I love my comments, and sometimes I have very lengthy events that become a bit visually muddled. If I could use comments within events as opposed to above them, it'd make organisation far easier and quicker.