I'm sorry for the delay with this question.
1) Please don't overwrite or rename the default GNS trainer database files
The GNS Trainer installs a set of database files by default here: C:\Program Files (x86)\Garmin\GNS Trainer\GNS\db
This folder is a "special" folder for Windows (Program Files) with specific user access rights for a reason.
Instead, the GNS V2 supports specific means and facilities so that you can override and redirect the simulation to any other fol
Environment variables are loaded up with the process (this is how Windows and most OS are working).
This means for any change to take effect if the app is running, you have to quit the application first (Prepar3d for example) then start the application again.
You can therefore edit your environment variables before or during program execution, but any change will only take effect the next time you run the application.
@Albert Welledits The latest installer gives you the choice to opt-in or opt-out using one more recent selected database file included with the installer.
Just run the installer over, opt-out the DB file replacement:
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