I frequently wish more programs would implement a UI as flexible as the one in Firefox, where you can just drag buttons around, add extra large dedicated button

I frequently wish more programs would implement a UI as flexible as the one in Firefox, where you can just drag buttons around, add extra large dedicated buttons for zoom, remove buttons you don't need etc. Even more flexibility would be cool as well in more specialized software, but I think FF does enough while not overwhelming the user with possibilities.