Classes, such as actor components, declared in plugin modules, are not properly loaded by ue 4.19. They seem to only work within the project used to create the plugin.
Create a blank plugin through the editor.
Create a blueprint spawnable component in this plugin.
Ensure this plugin can be added to blueprint actors in the editor.
Copy the plugin to a new project, ensuring it is enabled.
Open the project and try to add the component to an actor.
The class is not available in the editor.
The class was demonstrated to be working within its original project, but once the plugin is copied to other projects, fails to be loaded. This is not limited to components. This is also the case for structs, actors, etc.