Since the change in Android storage permissions that came with Marshmallow (6.0) not all apps are able to write and in some cases read the external storage. In particular are old apps that haven’t been updated for years.
With that said a good number of apps that are in active development also have problems writing to the external SD card. This is either due to the developer not enabling this option or due to some device specific issue.
It would seem therefore that the only “solution” is for one to get a device with a generous internal storage or better yet a device that has dispensed with the SD Card slot altogether.
Fortunately, this doesn’t have to be the case. Provided you have root permission this is something that you can resolve relatively quickly and have both newer or legacy apps write to the SD Card.
Enable Magisk ExSDCard Access Enabler (Oreo and Nougat)
1. To get started flash Magisk and install Magisk Manager if you haven’t yet. Your phone will require a custom recovery like TWRP to accomplish this.
2. Open Magisk Manager and in the menu go to Downloads and search for the ExSDCard Access Enabler module. Install then reboot to finish installation.
That’s it, no additional settings are required. After rebooting your external SD card will now be mounted in a new location: /mnt/media_rw/[SDCARDNUMBER]/
Define Path for App
Depending which app you’re using you now have to follow this path when selecting a directory (e.g. a download folder) in the SD Card. In some apps you may have to enter the path manually.
|SD path in an old version of Fora Dictionary|
To ensure this setting works properly keep the module enabled at all times.