As of v6.3.0 Dux-Soup introduces a number of system-tags that are used to track activity of, and activity on, a profile. At the moment the following 4 system-tags are used. These tags are visible when visiting a profile and when using the Tag-Search Tool.
After a profile has been sent a connection request, the robot will add this tag.
After a profile has been added as a connection, the Message Bridge will add this tag.
When a profile sends you a message, e.g. as a reply to your connection request, this tag is added by the Message Bridge.
When you first enable the Message Bridge, it will mark the then most recent connection on https://www.linkedin.com/mynetwork/invite-connect/connections/ . Any connections that are added later will be forwarded by the Message Bridge as INVITATION_ACCEPT messages.