This would be a new kind of programmatical shape that can be inserted into the document.
It consists of multiple areas for editing text, within a table. Cells of the table will resize as needed to fit the text (unless the cell size is constrained).
Look at Dia's UML widget for ideas of what this could/should do.
This should also be usable for implementing SQL tables for diagramming purposes.
Another example could be a cartoon, with cells containing text and graphics.