I am currently using the newest update of Spotify (7.10) and the storage icon in the settings disappeared. At the moment I am unable to set the general storage to my SD card, because of the missing icon. I tried to delete and reinstall the hole thing, but it doesn't help. I would be glad to get a good advice, otherwise I have to cancel my contract..
"Just make sure you have an Android/data/com.spotify.music folder on your external SD card. Once this folder exists, a new option Storage is available on Spotify Settings. There you can swith to SD Card. Worked for me on Adroid 5.0."
Someone else said to just go to that location and create a folder titled that.