Select Zoom inbuttonfrom the Zoom combo button on the General Toolbar JS and click on it as many time it is necessary.
Select Zoom out button from the Zoom combo button on the General Toolbar JS and click on it as many time it is necessary.
Scroll the mouse wheel over the canvas.
Click Zoom Allbutton on the General Toolbar JS to optimize the size of the structure to the canvas size.
Select Zoom to Selection button from the Zoom combo button on the General Toolbar JS to display only the selected structure on the canvas .
Appears when its needed: when the structure is bigger than the canvas or when some structural parts are out of the canvas.