I'm so impressed by this add-on that I had to share some praise.
This is by far the best tab manager/ bookmark manager I've ever used on Firefox or any other browser.
It functions like One Tab, Group Speed Dial, and a bookmark manager all in one.
Everything is intuitive and every icon does what you think it will do. The pinned tabs are horizontally laid out above the vertical list of the all of the unpinned tabs. You can create a group from those tabs and nest the pages. You can expand and expand the groups of tabs and create a new group. Everything has quick access. You can drag and drop just about anything. It's my pick for the Best Productivity Add-On of the Decade. And that's coming from a real add-on junkie. Thanks devs and or devettes!