More property type options for marketing emails

I need to create a property on marketing emails to assign each email with a unique tracking code that links back to our event registration platforms. It seems at the moment, I can only create multi-select or drop-down select properties, not the single line text property I need.

I note that some of the HubSpot-created properties for marketing emails are single line text so not sure why I can’t make these myself!

We need the full range of property types for marketing emails (and all other objects too!)