According to Poetry documentation:
In order to get the latest versions of the dependencies, you should use poetry udpate
And to update Poetry version in its current runtime environment, you can run poetry self update
But what is the command, or at least the recommended way, to update plugins, such as Polylith Plugin, once installed?
There does not seem to be a specific update command, as of the time of this post.
As suggested by sinoroc, you have to reinstall the plugin into its latest version:
poetry self add [plugin]@latest