Setting alarm ringtone on Google clock on Marshmallow Earlier (actually ... I do not know when that stopped working) when I would try to change the ringtone of my alarm from the Google clock app, I would get to choose which "source" I would get the tone from, there was a default list, and I could also choose a file from my own library.

Now I can only use the said default list. I have a tone that I had set by the described method in the list but I have no way to add anything to that list.

Are there solutions?
Install ES Explorer 

Play the tone using ES and follow steps to  set it as ringtone, notification or alarm. Selected track would be added to default options panel of ringtone/ alarm




Note: ES Explorer has privacy and security concerns, so if you are not aware of how to sandbox it and use it, uninstall immediately after this operation of setting ringtones