The effect of scale on canvas size
scale is the Parameter that controls how large of a Canvas you have to work on. Scale does not affect physics, so everything will behave as expected. Scale can be used as a way to "zoom" in on particles. First you must pause so that your creation does not get pushed over the edge if you move the screen, then you can change scale so that you can see better and work easier, then you must change scale back to the previous value, re-center your creation if you moved it, and unpause in order to not damage anything.
On OSX enabling the Parameter scrollFlag allows the bounds parameters which represent the in-game size of the canvas, to be separate from the viewWidth and Height parameters which represent the size of the window in the operating system. Sadly it seems as if this functionality does not work in Windows.