That's the only way commands are added. Every command on there was added by a plugin. You can see a simple example in the about plugin: a command is created at

That's the only way commands are added. Every command on there was added by a plugin. You can see a simple example in the about plugin: a command is created at https://github.com/jupyter/jupyterlab/blob/6d540709ad64e7767085eeb3e05d2d6f859333fe/src/about/plugin.ts#L158 https://github.com/jupyter/jupyterlab/blob/6d540709ad64e7767..., and is added to the command palette at https://github.com/jupyter/jupyterlab/blob/6d540709ad64e7767085eeb3e05d2d6f859333fe/src/about/plugin.ts#L173 https://github.com/jupyter/jupyterlab/blob/6d540709ad64e7767....