@Override
	public List<DataType> findDataTypes(String dtName, TaskMonitor monitor) {
		List<DataType> results = new ArrayList<>();
		DataTypeManager[] managers = getDataTypeManagers();

		// we put the program's data types at the front of the list so clients can tell if the 
		// types we have found already exist in the program
		DataTypeManager pdtm = getProgramDataTypeManager();
		pdtm.findDataTypes(dtName, results);
		for (DataTypeManager manager : managers) {
			if (!(manager instanceof ProgramDataTypeManager)) {
				manager.findDataTypes(dtName, results);
			}
		}
		return results;
	}
Create the actions for the menu on the tool.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/DataTypeManagerPlugin.java