Try to think if the sidebar is seriously needed or not. Because, for most of the common people it is not needed other than the ai chatbot feature. try the sidebar revamp command in about:config and make it false and see if it looks good and spacious, the more it is minimal the more it looks good, but also it should not lack features. The appearance due to the sidebar is not so good. Instead if firefox can give a chatbot button that will only appear in the home page and by clicking it, the selected chatbot will open in the sidebar. Or you can simply give a better option to the users to customize what to keep in the sidebar or just a sidebar enable or disable button. Frankly speaking, I don't think sidebar is needed and not having a sidebar is one of the reason google chrome looks better than other browsers. Please consider my request and take necessary action as soon as possible. Thanks For Reading.