did verify that it is a parameter:
http://www.customware.net/repository/display/AtlassianPlugins/list-data
It says "If true, a non-empty item must be selected." Initially, the list doesn't have anything under the first List-Option, its blank. But the form still saves anyways, and it doesn't require it.
The 'required' parameter does work on {text-data} just fine.
Below is a simple example of it not working. I am running on Confluence v 2.58
{list-data:Choose|required=true}
{list-option}
{list-option}Value A{list-option}
{list-option}Value B{list-option}{list-data}
{list-data:My Options|required=true|blank=true|blankText=[Select an option]}If the item is required and the '[Select an option]' item is selected, the user will be prompted to select a valid option. If it's optional, the current value of the list will be null.