UI-Scaling does not work, because I can not find necessary file

I am using PopOS and installed jabref with the apt package manager.

The installation manual explains, that if everything looks too small one should add the line -Dglass.gtk.uiScale=1.5 to the file JabRef.cfg. (Installation - JabRef)

I can not find this file, and it is not in /opt/JabRef/lib/app/JabRef.cfg. How can I find it?
(Or respectively, how can I scale Jabref? Right now, it is unusably small.)

The output of ddpkg-query -L jabref is:


@Sinthoras7 You seemed to have installed an old version of JabRef, the version 3.8.2 that is no longer supported. You can download the latest version here JabRef download latest version