The test-automation flaw can be next:
1. Clone the plugin registry repo: https://github.com/eclipse-che/che-plugin-registry
2. Customize https://github.com/eclipse-che/che-plugin-registry/blob/main/openvsx-sync.json
3. Build an image from these sources and push it to a registry
4. Patch the Che-cluster according to the documentation: https://docs.redhat.com/en/documentation/red_hat_openshift_dev_spaces/3.4/html/administration_guide/managing-ide-extensions#extensions-for-microsoft-visual-studio-code-open-source-adding-or-removing-extensions-in-the-embedded-open-vsx-registry-instance
5. Create a DevSpace and make sure that there is present just extensions form the patched openvsx-sync.json