I see you are using 5.5 .
To export the plugin, click on File-->Export-->Plugin Development-->Deployable Plugins and fragments
Once the plugin jar is generated it must placed in [CORTICON_HOME]/Studio/plugins location.
Doc link: documentation.progress.com/.../corticon_extensions.pdf
If this does not resolve the issue I'd encourage you to open a support case. Troubleshooting such issues is easiest through a support case .