A unique way to customize nametags
https://polymart.org/resource/customnameplates.2543
Open the project with your IDE and execute gradle build. Finally you will get the jar at /project/build/libs/CustomNameplates-xxx-all.jar.
Install JDK 17 and set the JDK installation path to JAVA_HOME as an environment variable.
Start powershell and change directory to the project folder.
Execute ".\gradlew build" and get the jar at /project/build/libs/CustomNameplates-xxx-all.jar.
Plugin is scheduled to be recoded on December. At that time API would be available. For the moment you can use the jar as local library.