The way it is on Linux and Windows?
Note this is a private Chromebook, not a Google for Work or Education one.
Chrome OS does not allow policy management locally since you don't have access to the profile or filesystem (like you do in Linux and Windows). you need to get a domain and enroll your device in it, and then manage the device via the admin console.
you can load extensions unpacked like any other OS -- unzip it into your Downloads directory, then go into the extensions page, check the developer mode box, then use the load unpacked extension button. a pita, but it works.