Tab Center Redux is the official successor to Tab Center: https://addons.mozilla.org/en-US/firefox/addon/tab-center-redux/ https://addons.mozilla.org/en-US/fire

Tab Center Redux is the official successor to Tab Center: https://addons.mozilla.org/en-US/firefox/addon/tab-center-redux/ https://addons.mozilla.org/en-US/firefox/addon/tab-center-re... It's now a WebExtension, which means it will work in Firefox 57+ (and possibly eventually Chrome, if they end up supporting the same APIs), and uses the new Sidebar APIs that the new Notes experiment also makes use of. If that doesn't fit your use cases, there are also quite a few new tab sidebar WebExtensions popping up that aim to replicate existing more sophisticated tab management extensions like Tree Styles Tabs (https://addons.mozilla.org/en-US/firefox/addon/tree-tabs/ https://addons.mozilla.org/en-US/firefox/addon/tree-tabs/), and others that try to innovate on their own terms, such as Sea Containers (https://addons.mozilla.org/en-GB/firefox/addon/sea-containers/ https://addons.mozilla.org/en-GB/firefox/addon/sea-container...), which makes use of the new Containers experiment. Overall there is a huge amount of very promising new development in the WebExtensions space, and this is exactly the kind of innovation I had hoped WebExtensions would encourage.