Within the gallery you can make it to were pictures will save by default on the SD Card. However, with the download of applications, these would have to be manually moved over to the SD card. There would be no way to make it to were it would install the apps and save them there by default.
Regards,
HD Tech
How do I make the SD Memory card my default storage device on my Tab 3 lite?
There is no option in settings or in My File to do this?

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