So for my phone storage optimisation, here's what I did to get my Samsung Galaxy Note 8 to use the SD card for most of the storage requirements of my Avare app:
Click:
{the Settings gear icon on top right of screen} then:
Scroll down and click:
"Apps"
Then wait while it loads up all the app icons, then:
Scroll down and click the icon for:
"Avare"
Click:
"Storage"
That will display a window titled "Storage used"
In grey font it will display "Internal Storage", so
Click:
"Change"
Click the radio button for:
"SD card"
That brings up a window titled "Export Avare" with some brief instructions etc. and then
click on the button:
"Move"
That brings up a progress bar window "Transfer Avare". Wait until that closes. It will return to the Apps listing.
Click on the app icon:
"Avare"
and verify that now in the "Storage" panel it displays:
"xxx MB used in external storage"
If you get that result, then you've achieved your objective! Most of the Avare data etc. is now stored on the SD card, freeing up main storage capacity in your phone.
And, it's a lot quicker and easier to do than it might first appear reading the foregoing, because I have given each little step in detail but really each subsequent step becomes pretty much intuitive once you get started.
Please note however:
(1) Thereafter, within the app when you click on:
"Menu" --> "Download" --> "Update"
the app will continue to use the SD card storage as you had selected.
(2) HOWEVER! Each time you Update the Avare App (best to do updates manually, using the Play Store), you will need to repeat those steps above to get the data transferred to the SD card; and within the Avare app you will also need to:
Click:
"Menu" --> "Download" --> "Update"
But, as with most challenging things, after you've done it once, all of these steps are a lot more intuitive and easier to do!
(3) My Samsung Galaxy Note 8 is running Android version 9
(4) Those same steps also work fine on my Samsung Galaxy 7 Edge running Android version 8.0.0
(5) BTW, those same steps also work fine to use the SD card storage capacity for many more of my apps, on both of those Samsung Galaxy phones.
(6) It will be helpful if other Samsung (and other phone/tablet types) users running other versions of Android can comment as to whether the foregoing steps work for them too.
I hope this will be helpful!