It's similar to the
<!--more--> tag, but used in the admin area, I guess. It's a script I've had for a while and used on various sites for expanding divs (like when people need to buy stuff, and divs fold out based on their choice of payment - that kind of thing) and I just decided to implement it in the admin area for clients. Works really well.
Like I said, I have seriously considered writing it all up as a plugin, I just haven't gotten around to it. Plus, I don't know if anyone else really would *want* such a thing, you know? I see a few people ask for something similar every now and again, but I don't know if there really is a huge demand for such a thing.
But if you're interested in it, I'd be happy to email you the script and a little bit of instruction on how to do it. It's really pretty easy. (If you want it - you can go to my website and email me from the contact form :) )