Hello xDDDDDDD
I would like to give a little suggestion, but will help a lot =P
After finished a sequence of animations, made with a character mosaic with more than 40 sprites, I accidentally deleted the first sprite, and this was the begin, hahahah, bored, I tried to undo this, but nothing happen clicking there, or better, nothing visible in the animation screen.
So, I believe, will be more intuitive if the undo and redo buttons happen to show inside the animation screen too.
No worry, the software still great as it is now, and I liked a lot the folder save system, where I did all my polygons without worries =P