Decent customization, the large lacking feature is the ability to hide all of your tabs up top.

The main reason I still haven't switched to Chrome

cool addon

This should be the default way of managing tabs for any desktop web browser. A must-have plugin.

Works well enough, but breaks in Nightly 74

mozilla

after using this, and accidentally found another add-ons called Sidebery. I think this needs to be developed further, because what is here is in the sidebery and even more features. Don't know why Firefox recommends these add-ons more than Sidebery