I'm sure you used to be able to do this in the good old days of OS9, but now I've got a Magic Mouse that can't be used when plugged in to charge, I wondered if this was an OSX thing I'd missed. Is there a way to tab through the buttons of an open window (say a File Dialogue Box) with keystrokes as opposed to using the mouse? I see that if you Cmd-Tab you can switch between open applications, but haven't delved any deeper than that so far. Can it be done. On the latest version of Sierra.