Keep Apps on SD card So I'm using Android 7.0 (build nr. NRD90M.G935FXXU1DQH5) on a Samsung Galaxy 7 Edge.

Whenever I update an app that I've moved to SD card, I need to move it back to SD card after the update.

This is very annoying (and been for a while). Any way I can resolve this without downgrading or rooting the device? Because I could have sworn there was a time apps moved to the SD card STAYED there.

(Personally, I would have no issue with rooting the phone, but certain apps - like for example used by my bank to authorise e-banking transactions - won't work on rooted devices, so let's not.)
Let me tell you a bit about the Android system. When an app is updated, the developer may not merely add files to its directories, but may also delete/modify existing ones. Android system is such that, Google Play Services framework cannot update apps while they are on SD card. So, the apps are always updated by first moving them to device memory, and then modifying/adding/deleting apk files.

Unfortunately, there is no system to automatically move the apps to sd card after update. There may be apps claiming to do that, but I haven't tried any, so I cannot tell.

On all Android devices, be it 4.0-Kitkat, 5.0-Lollipop, 6.0-Marshmallow, 7.0-Nougat or 8.0-Oreo, this system is unavailable. After update, you have to manually move the app back to sd card. Nothing can be done about that.

Please note that all methods mentioned here are on unrooted phone. I don't know what can be done on a rooted one.