Hotkey Toggling between Private & Non-Private browser window?
You'll find that shortcut in System Preferences &gt; Keyboard &gt; Shortcuts &gt; (left side of window:) Keyboard &gt; Focus on next window.

With my (German) keyboard default is Cmd-&lt;, but that may be different with other system languages. Just look there!

BTW: I changed this shortcut to a more convenient Ctrl-&lt; which (on my keyboard) is easier to reach.