Want to try the latest software for the Quarto? Then use the url
https://qnimble.com/package_qnimble_beta_index.json
in the Arduino Board Manager URL (see the Quick Start instructions but use the above URL instead of https://qnimble.com/package_qnimble_index.json.
You'll need to restart the Arduino IDE after changing the URL, but then when you go to board manager you'll be able to install the latest beta software for the 'qNimble Boards'.
For what's new in the current beta channel, please see the most recent beta announcement post.