Consider adding handles to the canvas so one can quickly resize the entire diagram (not ZOOM).
I see, sorry for misunderstanding. Take a look at this Knowledge base article which talks about maximizing canvas area:
But you brought a good concern, that we might to need to improve UI so it is more intuitive that user can maximize screen.
I does allow resize, but its not obvious. DON'T MAKE ME THINK - a good read btw.
There is feature available "Zoom to fit", which tries to fit the entire diagram in the canvas into single screen by automatic zooming and re-positioning the diagram. Please try that.
I believe some users might find it convenient to set the canvas to a specific size instead of zoom. The ability to resize is already there, just not obvious. Adding handles would help....see image.
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