Android 6 (cyanogenmod 13) external sd card write access
As I found out for now, there is no way to give such permission, except running whole application as root, and that ins't easy (or even possible?) without modifying application code, anyway, running apps with uid=0 is a bad idea anyway. The problem is, that in android 6 WRITE_EXTERNAL_STORAGE permission should be asked on runtime by an application, and if the application isn't Android 6-aware, there is basically nothing we can do. I hope that developers will adapt their application for new Android 6 reality soon.