Today Gary Rosenzweig at Macmost.com released a YouTube video demonstrating how to use Terminal to change the location where screenshots are saved on a Mac. I tried it & it works quite well. But I don't need that method to achieve the same outcome.
Once upon a time (sometime between 2005 & 2007) I acquired a preference pane called (very imaginatively!) Screenshots. With this you can save screenshots to any one of 12 different formats 
and vary the location as you desire.
Naturally, that Preference Pane is no longer available, but I can report that it still works under Sierra 10.12.3.