I have placed a shape with a connection point. If I drop a connector on the diagram then when moving an end near to the shape the connection point becomes visible.
If I have another shape with a control point that can be glued, when dragging this control point near to my other shape no connection point becomes visible. It then becomes pure guesswork as to where the connection points are in the shape.
The shapes connection points should become visible when anything that can connect to it comes near. Other than that it needs a way that can force the connection points to always be shown.