Yes, that is a mystery... But I do this: I use it (the Notepad), write with a keyboard and then (still with the document open) press "share" icon (in my device) up in the right corner and select Jota Text Editor (Another app that I instaled) that allows me to export, and save the file.
(
https://play.google.com/store/apps/d...o.pandora.jota)