Android to Mac is pretty mysterious, it doesn't show up in Mac Photos (of course) nor does it show up as a USB device so you need to:
- Download Android File Transfer
- When you plug your Marshmallow phone in, it should pop up the USB transfer select dialog and you pick File Transfer to get a file view
The problems I found are:
- You can get stuck in "locked" mode. That is even though the phone is unlocked, the "locked" icon still shows up. I had to reboot the phone to fix.
- If you plug it in the first time you won't get the dialog. With Marshmallow, they seem to have move the dialog. It is no longer in Settings/USB & Storage on the upper right. You have to touch the tiny status bar at the top and then USB Transfer appears as a notification item.