Actually you don't even have to add more data. The size of the list is defined by this property in widget.properties
# Default number of items to be displayed per page in a list form
Locally you can change that by hand, clear caches, et voilà.
Now if we would like to have the same on demos we would need to have this property in the DB and use EntityUtilProperties.getPropertyNumber() to retrieve where it's done at the moment. Unfortunately EntityUtilProperties.getPropertyNumber() simply uses for the moment UtilProperties.getPropertyNumber() so it means more work than adding those data. But once done, it's for all (though you would still have to replace the calls where UtilProperties is used instead of EntityUtilProperties. I don't remember if we have an umbrella task ans subtasks for that. It seems though a long term work, because we have much properties likely to benefit from this possibility.
Another KISS option: maybe simply testing locally is sufficient