I don't know if this could be possible, but instead of having the top sidebar with a fixed search bar to the left, it would be nice if we could have a search button which opens a sidebar "on hover" or even open the search bar by opening a new tab (default behavior, but if search bar is not used, it will be hidden).
It is not possible since #urlbar and #TabsToolbar are child of two different containers. It is impossible to dynamically resize both when one of the two is hovered.
I don't know if this could be possible, but instead of having the top sidebar with a fixed search bar to the left, it would be nice if we could have a search button which opens a sidebar "on hover" or even open the search bar by opening a new tab (default behavior, but if search bar is not used, it will be hidden).