In general, you can add tracking codes to your Event through our Custom Code feature. However, we are aware that Facebook released a new update where Users have to approve domains to be able to add and track Pixels on a page. This means you won't be able to add Facebook Pixels to our pages at this time until we are able to address this update in Demio. 😔
You should be able to add a Facebook Pixel to your custom pages and track conversions that way!
Note: Tracking Registration page conversion for On-Demand-only Events with a Facebook Pixel may be trickier. Since On-Demand-only Events do not have a Thank You page and Registrants are redirected to a Demio webinar room page as soon as they sign up, your best bet may be to track the button clicks on your custom Registration page where the Demio Registration form is embedded.
One other option would be to set up Custom Domain that you can verify on Facebook to use Facebook Pixels on Demio pages directly.