Is there a way to add conditional text to the Summary Page Descriptive Text?

Summary:

I am trying to add conditional text that is if Preferred Name is Null then use First Name. I am typing in my logic into the source code, but it disappears after saving. I also tried pasting it into Rich Text but I get an error message when saving it. Lastly, I tried creating a field, but it requires a compensation item. Am I missing a step?

This is the logic I am using based on this document:

Ways to Configure Statement Text

<?if:Preferred Name?><?Preferred Name?><?else?><?First Name?><?end if?>

This is what is needed to create a conditional text: