It sounds like you might need to use the Node Edit Tool. For lines and segments, once the path is closed they become a single object - even if not grouped together. The individual nodes can be edited to change length, change curves, move node points around while still connected to the rest of the object, etc. And if the objesegment wont change - it may need to be converted to a "Curve" or the Node changed to a "Cusp". This allows editing of individual nodes, whereas otherwise, they are treated as a "Line" (no curve "handles") or a "Smooth" node.
Lastly, the connector line tool is a unique tool that will not allow editing like a standard line or node - it has intrinsic properties that make it behave under its one rules. The only node editing that can be done with the connector tool is to move the nodes in various directions to keep the connected line segment in tact - no curves and no node editing.