Getting to grips with CC3.

I want to make a continent map but am significantly challenged by one hurdle.

From first impressions it appears that you have to make the entire continent in one go. For example, once you start you cannot stop a line, zoom in a little draw some more, zoom out and carry on. Each time you stop a ‘land mass’ is created and I cannot see where or how you can join two together i.e continue a land mass from a previously created one? It seems quite unreal that anybody can freehand draw an entire world 2000 miles wide without lifting their finger off the mouse!

Is it possible to add to en existing land mass without the ‘coastline’ of each one showing on top of the other?