This boils down to a question how to invoke a certain page of the extension from the command line. The SSH extension can be invoked by
"C:\Program Files\Google\Chrome\Application\chrome_proxy.exe" --profile-directory=Default \
--app-id=iheocdlapopnjhneafdihoapcfncnbbf
which is the regular shortcut created by Chrome. But I couldn't figure out how to invoke Mosh that's bundled with it.
Inspecting the Mosh link in the extensions menu using Chrome's dev tools leads to nassh_extension_popup.js, and reading the code suggests that the desired URL is chrome-extension://iheocdlapopnjhneafdihoapcfncnbbf/plugin/mosh/mosh_client.html?promptOnReload=yes&openas=#profile-id:mosh. But Chrome doesn't accept the URL as an --app-id argument, and neither works passing it as (another) argument or experimenting with other similar flags.
