Yeah I hopped back over from Edge when the manifest v3 stuff came out, and the two main things I miss are proper profile management and vertical tabs - I’ve been using https://codeberg.org/ranmaru22/firefox-vertical-tabs to get around it currently, but having a native implementation to both issues will be a massive (and recently rare) Firefox W.
Really looking forward to this once it’s complete! I’m currently using ranmaru22’s vertical tabs, but having something native that won’t risk breaking with FF updates will be nice.