The datasette CLI tool currently has 7 subcommands: serve, inspect, install, package, plugins, publish and uninstall.

A plugin hook could allow plugins to register extra subcommands.

I've avoided this for quite a while because I didn't have good use-cases for it - but the existence of the datasette install xxx command for installing packages into the correct virtual environment means that actually there's a good reason to do this: it would allow plugins to provide additional command-line mechanisms without the user having to understand how virtual environments work in order to install those commands into the same environment as the rest of Datasette.