Right-CLICK a swimline and then click Insert ‘Swimlane’ Before or Insert ‘Swimlane’ After in the shortcut menu.
Hold the pointer over a corner of ONE of the swimlanes. Click the blue Insert ‘Swimlane’ Shape arrow that appears.
On the Cross-functional Flowchart tab, in the Insert group, click Swimlane. A swimlane is added after the SELECTED swimlane, or at the END if no swimlane is selected.
From BASIC Flowchart Shapes, drag a swimlane shape to the boundary of the band where you want it to appear.