Custom event parameters not being sent

Question

First off: I'm very new to Google Analytics!

I'm trying to use GA to track a custom event with some custom parameters, but I'm not doing very well. I've set up gtag.js according to this and it is working if I only set the following parameters:

function trackOutboundLink(url) {
        gtag('event', 'click', {
            'event_category': 'outbound',
            'event_label': url,
            'transport_type': 'beacon',
            'event_callback': function() {
                document.location = url;
            }
        });
        return false;
    }

But I would like to set some additional parameters and according to this it should be possible:
"You can add custom data, in the form of additional parameters, to any event (recommended or custom)"

I'm setting up GA using this:

    <!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=MY_GA_TRACKING_ID"></script>
<script>
    window.dataLayer = window.dataLayer || [];

    function gtag() {
        dataLayer.push(arguments);
    }
    gtag('js', new Date());

    gtag('config', 'MY_GA_TRACKING_ID');

</script>

And I'm calling gtag() the following way:

function trackOutboundLinkWithCustomParameters(label, version, url) {
        gtag('event', 'click', {
            'event_category': 'outbound',
            'event_label': label,
            'transport_type': 'beacon',
            'mobile_app_version': version,
            'download_url': url,
            'event_callback': function() {
                document.location = url;
            }
        });
        return false;
    }

If I break at dataLayer.push(arguments); and prints arguments I get the following (which is what I want to track):

But after having installed GA Debugger it seems it ignores my extra parameters when sending the tracking data:

Bottom line is: I can't see the additional info I provide about mobile_app_version and download_url in my GA dashboard.

Help!

Answer 1

Any custom parameters that you want to see in your standard reports will need to be configured before you send your data in with your event (cf. https://developers.google.com/analytics/devguides/collection/gtagjs/custom-dims-mets#send-custom-dimensions), so in your example, you should have something like this:

gtag('config', 'MY_GA_TRACKING_ID', {
  'custom_map': {
     'dimension1': 'mobile_app_version',
     'dimension2': 'download_url'
  }
})

Make sure you have already configured what the custom dimensions are.