You can extend the Developer Portal by creating and installing custom modules, or installing additional Drupal 9 contributed modules.
Modules provide functionality to your site, and the core modules that are included in the standard Developer Portal installation, provide all of the basic functions that most sites need. However, some of the core modules are not enabled by default, so you might want to examine the module list under the Extend menu of your site, to see whether the functionality you require is available from a core module before starting to investigate custom and contributed modules. If you still require additional custom or contributed modules, consider the following topics to help you create and implement modules consistently.
Note: The Developer Portal contains a Rules framework for event based actions. Some of those actions and triggers might exhibit unexpected behavior. A workaround is to create a custom module instead, because the same events and actions are possible there.