The SavePropertyDialog class is currently only used by AbstractVisualizer. It seems unlikely it will be needed anywhere else, and anyway the get/set methods for the saveConfig field don't really make sense. The config is passed in via the constructor. If the setter were dropped, the field could be made final. Not much point having a getter either as the field is provided by the caller.
This issue has been migrated to GitHub: https://github.com/apache/jmeter/issues/3905