Yep. To turn it on you type "bb.moveobjects on" and to turn it off you type "bb.moveobjects off" (without the quotation marks in both cases and the only space being before the words "on" and "off").
Things placed with it on will stay in place even once you turn it off, as I said above. And you don't need to turn it on to move them to normal placement locations. Just grab them and move them without it being on. Though, if they were raised or lowered with the 9 and 0 keys, you may need to turn it on just to lower them to the ground level if they aren't something that "snaps" automatically to the correct level.
Oh..and if you do need to turn it on, don't forget to turn it back off. I use the gallery a lot and regularly have to fix these kinds of things to make a lot playable....I also almost always forget to turn it back off until I'm doing my own thing and notice I can put things inside walls and whatnot. *sigh*
