I feel that the private browsing markers aren't enough to distinguish the windows in private browsing mode. I would like windows in private browsing mode to have an entire different theme than the normal windows. Is there a way to apply a theme - say the default dark theme - to only private browsing windows, and keeping the normal windows on a separate theme? Currently I'm solving this problem by using a custom userChrome.css file, but I get the feeling that those are going to be deprecaded and stop working. I would like to find an officially supported way to solve this problem instead. If no such official way can be found, where can one submit a feature request for it? :D