You can add lanes to existing pools and lanes.
When you move or delete objects the size of pools and lanes adjusts automatically.
Lanes and pools can only be selected by clicking their border or name as soon as objects are placed in them. When you delete a lane, the size of the pool (or the wrapper lane) decreases automatically.
Procedure
You have added one or multiple lanes above or below.
Tip
To add lanes you can also click the icon for adding. It is displayed when you click in the lane header.