How to add variables to config

I'm trying to do something really simple: add a custom variable to every page hit which I can filter in Adobe Analytics. I know how to use JavaScript, but I couldn't find any documentation for how to add something like "developerId" to the set of data sent to Adobe.

Here's what my code looks like:

insertJS("https://az725175.vo.msecnd.net/scripts/jsll-4.js", () => {
    const config = {
        coreData: {
            appId: "PlayFab_gamemanager_prod",
            market: "en-us",
        },
    };
    awa.init(config);
});

Thanks!