What setting do I need to be able to log into QD-Scan with a barcode?

This can only be set by a local administrator.

Local administration > Access guard.

Select here "Give users the ability to log in with a bar code.

Open

As mentioned here in parentheses "there is always a check for IP address.

Click on Add IP Address.

Open

You will now see an IP address filled in, click save.

In the settings of your user, if you open the name, you will see the "Print barcode login" button.