Guides work well for the aligning a top with a bottom or a left side with a
right side (drag a guide off the ruler). Theoretically, a guide is similar
to a "dummy line," but it's setup to have the edge of a shape easily snap
and glue to it.
For connection point alignment, how about making the connection points
inward/outward while you're positioning the shapes, glue the connection
points to each other, and then move the shapes horizontally or vertically
back to their proper position with the arrow keys?