Multiple canvas can help to display images over multiple videoprojector without being bored with the exceed of images on the edges (which is not the case if you "share" a canvas with several projector: a big image overlap on several projector). In many cases, timeline is useful to quickly edit and synchronize over the time what happen on several projectors (that are display through several canvases). Multiple canvases for the timeline is essential to use the canvases feature unless we have to go back to Millumin 1 process.