On the page you reference, the first section "Creating and Editing Swimlane Diagrams" has paragraph titled "Editing the label of a row or column" that says:
Editing the label of a row or column
The label editor can be opened by double-clicking the row's or column's label.
But (depending on the value of the label's "Placement" property) such a label may be moved to any other position as well. There are two ways to move a label to another position:
Finally, swimlane tables are group nodes. Thus it is possible to assign other nodes as child nodes to swimlane tables. This may be done by dragging node templates from a palette section right onto a swimlane table or by pressing and holding SHIFT and moving an existing node into a swimlane table.
On second though, I would like to mention that swimlane tables are not meant to present tables of text. Swimlane tables are meant to organize other nodes (i.e. the swimlane table's child nodes) in a tabular fashion.
If you want to have a table with text contents only, create a normal (rectangle) node and use HTML formatting in said node's label. See How can I achieve different text stylings within one label? for more information on HTML formatting.