1. Open your custom declarative component project.
2. Add the desired attribute and deploy it to your desired path.
3. Stop the running wls.
4. Open your main project ( consumer project). Go to properties.
5. From the libraries and class path delete the existing entry for the component.
6. Save the changes and close the jdeveloper completely.
7. Open the consumer project's ViewController.jpr in a text editor.
8. Remove all the entries containing any reference to your custom component library.
9. Reopen jdev and then go to resource pallet.
10. Add a file system connection and select the directory you generated the custom declarative component jar.
That's it. It should reflect your new updates component nicely.