Figurepool can be very handy for mindmapping, actually the 'fork icon tool' was added with mindmaps in mind, you just click the icon tool and a new already connected box is added. Just double click the box to add new text label to it.
The scrolling issue seems to be an OS X related bug. I sometimes observe the same. The fact that sometimes two finger swipe is recognized as back button is a Google Chrome on OS X feature. I was able to get around the zoom/scroll issue by pressing the Shift button. Not sure if it'll work for you though. At least you can give it a try...