I appologize for not replying to you sooner. I have been busy with many things and hadn't logged into my account here in a few weeks.
What would you think of having an access to add-ons MUCH more straightforwardly ? Maybe icons directly at the top of the burger menu?
I had tried something similar in order to move the new-tab button into the Tab Manager Menu, but it unfortunately doesn't seem possible. Menu items can be re-arranged and hidden, but they cannot be added to a menu or moved from one menu to another. I agree though that your idea would be really cool if it could be done.
Or icons on display next to the URL field, with a sliding bar letting you browse all the way to the end?
I don't think this is possible with CSS code either, so I can't help, but I found a post on reddit that involves javascript: