Change iPhone backup location permanently? I have 20GB left on my OSX Macbook Pro so I bought the Transcend JetDrive sd card for extra memory. 

The iPhone iOS 10 back up takes about 80GB and would like to move it to that external memory drive. Moving is not a problem because I can manually locate the file, but is there a way to automatically backup my iPhone to that new location?
The usual solution to this is to use a symbolic link to redirect your iTunes backup folder to the external drive. There's a discussion of it here: Is it possible to backup iOS devices to an external drive?