According to the Downgrading / reverting to a lower version article, you have a Windows service install.
Does that sound correct? It would be visible as a service, run at boot, and allow access to all accounts.
You would have had to run Duplicati.WindowsService.exe by hand after a .msi install to get that set up.
If you do in fact run as a service as SYSTEM
user, then that would have permissions for almost anything, however updates can get there in other setups. Does Task Manager show Duplicati.WindowsService? What user is it? On Database screen, is yours in your own user profile, or in a C:\Windows subfolder?
It’s not a folder, it’s a file. If it was a folder, that would also have created a problem when editing as a file.