Anaconda add-on custom installer


I am trying to create a custom installer for Rocky. I followed this guide (Chapter 5. Developing installer add-ons Red Hat Enterprise Linux 9 | Red Hat Customer Portal) to create a custom bootable image ( I used the last Rocky iso as a starting point).

I downloaded and put into my image the example add-on from GitHub - rhinstaller/hello-world-anaconda-addon: UNDER CONSTRUCTION! A simple example of an Anaconda addon and I expected the plugin to show like in the image here

but I am unable to load the plugin.

Has anyone some idea or some more documentation on how to create a custom installer with add-ons (the documentation online is very poor)

Thank you.