Re: Moving apps to SD card
I've always had issues with Samsung devices and SD Cards. I just use them to store files now, I lost some vacation pictures once when I didn't have connectivity to backup to Dropbox.
But yeah, that icon shows if you unmount the SD card (or if it's failing, it unmounts itself). Also, I'm not sure if the Note 4 does it, but the Tab S does. Whenever you reboot, it unmounts the SD Card and then remounts it AFTER reboot. Might not help for apps installed on SD Card.