Hi @Stephen721, let me see if I can help out here.
There is no way to change the default memory in the phone to the SD card instead of the internal storage. There ued to exist a feaure enabling you to move apps to the SD card which was removed from Android, but Sony Mobile continued to support it for users' convenience for some time. However, we decided not to keep our solution to move apps to an SD card for users' security and privacy. So we stopped providing this feature in the Xperia XZ1 series, XZ2 series, the Xperia XZ Premium, the Xperia XA2 series, Xperia XZ3 and newer products.
We do recommend users to move photo, video and music data to an SD card to save storage space in the internal memory. In phones that don't have this option in the device setting, you can move files manually using the pre-installed Files app or a file manager app of your choice from Google Play Store.
You can also choose to have the SD card as default storage for pictures and videos taken with the camera app. In order to do this, open the camera app Tap the cogwheel icon > Tap Data storage > Choose SD card.
I hope that answered your question!
