As indicated in the documentation, it states that the correct technique is to have 2 lanes, first.
Pools and lanes are added via the modeling element Pool/Lane:
- Select the Pool/Lane entry in the shape repository on the left side.
- Drag the element to the desired position.
- Create an additional lane beneath an already existing lane.
A lane is added between 'Central purchasing' and 'Department'.
- Create a sublane that splits an existing lane into two sublanes.
Before: The 'Central purchasing' needs to be subdivided into two organizational units.
After: The sublanes have been created and can be named now.
- Drop the element onto the canvas at its new position.
- Insert a title for the lane or pool created.