Mount Android Phone on Desktop
Use Android File Transfer, created by Google itself, and it gives you a Finder window to at least transfer files via USB connection. I noticed, however, that you have to use the Samsung cable they provide to power the phone, and not some cheap knockoff USB cable.

It would be nice to have a way for the icon to mount on the desktop via a Bluetooth connection -- but that's just not possible yet.

There is also the free Handshaker application in the Apple Store that is more full-featured and intuitive than Google's Android File Transfer. So far, it's looking like my best option and I don't see quirks except that I had to enable Android Developer Mode and then turn on USB Debugging on, as well as uninstall Android File Exchange because it conflicts with it.