The extensibility concept provides a very high flexibility of extensions. However, flexibility leads to complexities. There are different extension options. You should look for specific places where SAP has enabled extension points. Check if you can meet the extension requirements by using one of the following options:
i18n Resource Extension
Controller Extension using a Hook
Where these options are not sufficient to achieve a given requirement, check the following options:
Only use these options as a last resort for achieving extensibility use cases.