SmartDraw has two kinds of Quick Add Controls.
One for diagrams with regular structure like org charts and mind maps. And another for more free form diagrams connected with lines like flowcharts and software diagrams.
In both cases, the Quick Add Controls help you build your diagram.
In an org chart, the Quick Add Controls are the yellow arrows that appear as you hover over the shape:
Clicking on a yellow arrow in the direction you want to add a shape will automatically add the selected shape in your library and connect it with an automatic connector to the previous shape.
For free form diagrams like flowcharts and software diagrams, the Quick Add Controls are shaped like yellow dots and let you draw a line and connect a new shape at the end of it.
Hover over a shape until you can see yellow dots appear along its perimeter. Move your cursor over any of the dots until your cursor looks like gray crosshairs, then click and draw a line in the direction you want to add a new shape. Once you're happy with your line, choose a new symbol to connect to your previous shape from the auto-prompt menu of common symbols.
If you wish to turn these Quick Add Controls off, simply deselect Display Quick Add Controls in the Options tab.