The canvas can be scrolled using the scroll bars at the right and bottom. These scroll bars respond to mouse wheel movements too. You can also scroll by holding down the Option or Alt key and dragging the canvas using the mouse.
If you customize the document toolbar and add the Tool toolbar button you can use a special hand tool to move the canvas.
You can zoom out the canvas to display more objects simultaneously by using the zoom control in the toolbar. If you have a multi-touch trackpad you can use the standard pinch zoom gestures. SQLEditor can zoom down to 5%.
You can have more than one document window open at once. To switch between different windows either click on the window you want or use the window menu to choose a different window.
To learn about how to create and edit objects see Creating and Editing Objects.