Well until now nobody has complained about bookmark size, but well, truth is, monitors are bigger now and it might become a little problem. The fact is, bookmarks can't be edited, you can only delete them all.
About horizontal scrollbar. Well there was no logical way to insert it. You can make a few hours lasting show in Fiesta, so most of the time the scroll gripper would be very small. Anyway when you get used to use Ctrl+mouse wheel to zoom in/out, it's easy and very fast to move around the show.