How do I send email to scouts/parents of a certain rank

I want to send emails to Scouts/Parents that are working towards a particular rank. How do I create an email group of just scouts holding a particular rank? Right now I have to scan and click each scout and parent everytime I want to send an email about forthcoming rank advancement work for a particular rank.
How do I sort Scouts in Scoutbook by rank?

There’s no way to sort by rank in the Send Message interface.

One option would be to install and use the Feature Assistant Extension for Firefox and Chrome to create a custom group. First, create a rank report (or otherwise determine the rank of the scouts). Use that list to select the relevant scouts in the Send Message interface and use the extension to save the group. It only saves locally, so you’ll have to copy the saved list to any other computers you use. It’s static, so you’ll have to actively maintain the list as scouts change ranks.

https://discussions.scouting.org/t/feature-assistant-what-is-it/98647