Properties: Connections inspector
Use this inspector to control how objects connect to one another.
The pop-up menu at the top of the inspector contains a bunch of magnet presets you can choose for the selected shape object. Magnets are points on a shape object that attract connection lines. You can choose to have no magnets, magnets placed according to cardinal directions (North, South, East, and West), magnets on each vertex (corner), or a certain number of magnets on each side of the shape.
If you select some number of magnets per side, then hold Shift while opening the pop-up menu and selecting another number, the two numbers are added together; you can get up to 10 magnets per side in this way.
Of course, you can always use the Magnet tool to customize a shape's magnet arrangement.
Deselect the Allow connections from lines checkbox to make it impossible for connection lines to use the selected objects as sources or destinations.
If you have a group or a table selected, you can choose whether connection lines should be allowed to connect to objects in the group or only to the group as a whole.
If you have a line selected, the Lines checkboxes become available. Deselect the Allow connections to other objects checkbox to make it impossible for the line to have an object as its source or destination. Deselect the Allow shapes to become labels checkbox to make it impossible to drag a shape onto the line and make it a line label; existing labels stay attached.