When I need this sort of thing, I usually just add a custom property to the parent container.
Example:
• Right click on the parent container and select "Customizers --> Custom Properties"
• Click the plus icon on the left, give the new property an intuitive name, and in this case, select the dataset datatype:
Result:
This eliminates the need for a hidden component, and the labelData = code becomes simply:
labelData = self.parent.labelData
The path to a jfree chart's xyPlot dataset is simply chart.plot.dataset, but for what you're wanting, populating the desired labels directly seems simpler and more maintainable. I would probably just switch from a power table to a custom property to get rid of the hidden component and otherwise keep using your current approach.