I have recently released a new version (v1.3) of my Trello Card Counter Firefox Add-On on the Mozilla Firefox store.
What's new in v1.3
This version brings a lot of changes with a new feature (average number of cards per list), adds more security and lays the ground work to make Trello Card Counter a cross-browser extension.
Detailed changelog:
Create new button showing average number of cards across all lists in the board.
Laid ground work to make add-on cross-browser compatible by using the browser-polypill library.
Correct permissions from all open tabs to just “trello.com” subdomain
Screenshots
Download
Check out on the extension on the Mozilla Firefox Add-Ons store here: https://addons.mozilla.org/firefox/addon/trello-card-count/