How to set a tag in API that can be viewed in Wordpress Matomo Analytics Page?

The endpoint in the HTML snippet for sending tracking data to the Wordpress Matomo plugin on my server is like below:
wordpress/wp-content/plugins/matomo/app/matomo.php?idsite=1&rec=1

How could I modify it to pass in a separate unique id/tag that I could use for distinguish between different traffic.
Regards.