Sometime we need to export a variable in Debian GNU/Linux, but we also want to export them permanently.
To export a variable temporary, for example QTAUTOSCREENSCALEFACTOR=0, we can run this command:
export QT_AUTO_SCREEN_SCALE_FACTOR=0
If we want to export it user wide, we can add that command mentioned above to this file $HOME/.bashrc.
If we want to export it system wide, we can add the following line to this file /etc/environment:
QT_AUTO_SCREEN_SCALE_FACTOR=0
We need to caution about that, the line in the /etc/environment should NOT include the export command.
Have fun. Be free.