Updated June 8th, 2019.
If you Control-click on the toolbar in Safari you’ll get a nice little menu that lets you customize it. Try adding Zoom In and Zoom Out buttons, and maybe a Print button, and maybe a Home button. Just drag the buttons you want right onto the toolbar (and drag the ones you don’t want right off). You can customize the toolbars for the Preview and Mail apps the same way.
All it takes a a Control-click. Or a right-click, if your mouse is set up that way. And the click has to be in the Toolbar itself. You can even Control-click on a button if you’d like. Try it and see.