HTML Editor, Layout Elements and Design Toolbox are all on the left side now, (instead of inside the simulator). The simulator is now just that and only the simulator. This is a much cleaner approach to design and layout.
Testing has shown this approach to be a much more stable environment. In the past it was possible to lock up the simulator by doing too many changes too fast. You should now experience much less wait time while testing updates. Give it a try.
This requirement is extended to all EU residents whether or not you are actually In an EU country. Which virtually means every website in the world should comply.
For the webmaster that means a lot of work and research. Which miappmaker.com has done over the past week.