Delete a link
Wired the wrong two ports, or the topology changed? Click the link to select it, then delete it - the two devices stay exactly where they are, only the wire between them goes.
Click the link itself (the wire, not either device) to select it - it highlights and the Inspector switches to show that link's details.
Right-click it and choose Delete, or press the Delete key while it's selected. The link is gone immediately - both PCs are still there, just unwired.
Deleting a link removes the real connection netplex. built for it, along with any port settings that depended on it. To reconnect, draw a new link the same way as the first time.