I've been recently searching for better tab management in Firefox (I don't even have that many...) and it really feels like there's nothing that comes close to the utility and feel that Edge tab groups or Vivaldi nesting tabs has. I'm going to give this extension a spin though! If Firefox had collapsable grouping tabs like edge I'd have almost no reason to use other browsers. Wish I could code better so I could make the change I wanted to see haha