Firefox extension. Lets you choose an account container from omnibox and opens a new tab in it.
Visit the extension page to add it to Firefox.
In omnibox, type "&", followed by a space, to start searching available account containers.
To build from source, install dependencies with yarn and run yarn build. Build artifacts are stored in web-ext-artifacts. See package.json for build dependencies. Tested on macOS Mojave 10.14.3, running yarn 1.13.0 and node 10.15.0.