Yes, you can certainly add your own tracking pixels to emails designed our system!
Navigate to the CODE section of the Drag-and-Drop Editor. If you have HTML editing permissions, you should be able to access the code of the file.
The pixel should be an <img> tag placed at the very top or very bottom of the HTML tab of a file.
We do not recommend editing the HTML code of a Drag-and-Drop Editor email file. Should you need assistance with a designed email file that has edited HTML, investigation and/or a resolution could result in billable time.