When you hit the hide buildings button, it will bring up an elven architect style grid of your city, you can toggle between hide and unhide, but when you touch a building that is hidden, it will reappear, and you can move it to a vacant part of your city
makes moving things around much easier on the app, and also finding those precious unused squares is a breeze
I don't play on the app much, but might start doing city rearranges this way, really like this new feature