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ComponentAddButtons (package info.openrocket.swing.gui.main) - manages the buttons for the components.
module-info.java (package info.openrocket.swing) - the Shapes class should be in the provides clause.
RocketComponentShapesService (in the directory swing/src/main/resources/META-INF/services) - the Shapes class should be in the list.
DocumentConfig - should contain an entry in the constructors HashMap as well as several entries in the setters HashMap to create the MyComponent from an XML description that would be written by MyComponentSaver.
We have implemented these steps for two new components, TabControlledTrapezoidFinSet, and AirbrakeSet. See those individual pages for more information.