Well I had to recognize that's a really specific patch , it allow you to export part of spritesheet under a sequence of file (png in that case but you can change that easily). I was searching for a software like that without find any good solution, (no transparency or sequence exporting)
I've done a easy GUI for it. there is some imporvement to do for exemple I don't really understand why the size of the LCD in presentation mode is so messy and it could be easy to do a kind of preview using matrixset.
Do not hesitate to improve this one and if something isn't clear tell me.
Have a nice day
Some good site were you can find sprite sheet :
an exemple of spritesheet :