This project demonstrates a way to carry project data across calls to ProjectSettings.load_resource_pack().
For instance, if you have a self-updating game, you'll need to carry the release version number across multiple instances of PCK files loaded by the engine.
One might think that ProjectSettings will be automatically reloaded from project.godot when a new PCK file is delivered. That is not the case! We can, however, manage changes using a ConfigFile saved in the user:// filespace, as seen in the func _version_by_config example.
Another approach is to store a special file in the user:// filespace containing your mission critical data. This can be seen in the func _version_by_file example.