public void edit(Composite composite, String fieldName) {

		CompositeEditorProvider editor = (CompositeEditorProvider) getEditor(composite);
		if (editor != null) {
			reuseExistingEditor(composite);
			editor.selectField(fieldName);
			return;
		}
		if (composite instanceof Union) {
			editor = new UnionEditorProvider(plugin, (Union) composite, showUnionNumbersInHex());
		}
		else if (composite instanceof Structure) {
			editor = new StructureEditorProvider(plugin, (Structure) composite,
				showStructureNumbersInHex());
		}
		editor.selectField(fieldName);
		editor.addEditorListener(this);
		editorList.add(editor);
	}
Displays a data type editor for editing the given Structure. If the structure is already 
being edited then it is brought to the front. Otherwise, a new editor is created and 
displayed.
@param composite the structure.
@param fieldName the optional name of the field to select in the editor.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/editor/DataTypeEditorManager.java