Click Pick random pair to select two lines; a snapshot is added to your record. Use the snapshots to summarize: what relationships can two lines have?
Your record — scroll horizontally to see all snapshots. Click a snapshot to select it (click again to deselect). Then move selected ones into a group below.
Select snapshots above, then click Move selected to Group 1 (or another group). Add more groups when you need them. Click a snapshot in a group to send it back to the record.