Hi, The people who answer questions here, for the most part, are other Firefox users volunteering their time (like me), not Mozilla employees or Firefox developers. If you want to leave feedback for Firefox developers, you can go to the Firefox ''Help'' menu and select ''Submit Feedback...'' or use [https://qsurvey.mozilla.com/s3/FirefoxInput/ this link]. Your feedback gets collected by a team of people who read it and gather data about the most common issues. Personally, I think that sidebar tabs is too radically different from other browsers, so I'm not sure that it would catch on. Nevertheless, you are welcome to submit your feedback.

See also; *Tree Style Tab https://addons.mozilla.org/firefox/addon/tree-style-tab/ *Tree Tabs https://addons.mozilla.org/firefox/addon/tree-tabs/ *Container Tabs Sidebar https://addons.mozilla.org/firefox/addon/container-tabs-sidebar/