Got it.
It's working now with Xiaomi file manager.
Unfortunately I don't know why.
Able to go to
Internal storage/android/data
Get message
Can't access items, try using android storage access framework
Underneath is an 'open' button.
It opens another window with file-manager
Internal storage ...

Tried to install miphoneassistant in order
to connect the tablet to pc.
Also copied miphoneassistant.res in the
installation folder.
But it's not working.
Can't lunch assistant and pc is not
Recognizing the tablet.

Tried to install Mixplorer
Didn't install
Message: app not compatible with tablet

I want to copy my project from tablet to pc
Xiaomi file manager doesn't get access at all to
Internal storage/android/data
Another file manager has restricted access and it to
Internal storage/android/data/com.eteks.sweethome3d.mobile
How can I change authorization, to access my .sd3x file,
In order ...