Yes, Preheader is only in Email Editor 2.0. You should switch! API support will come in the next release and there is no other reason to wait!
I am also having a problem with pre-headers in an Email 2.0 email. They're not populating in my preview email (Gmail), and when I search the HTML for the text of the preheader, it doesn't come up with anything. I double-checked that the preheader was enabled. Any thoughts? Justin Cooperman
Can you send me an email with a link to the email asset in your Marketo subscription. I'll have to take a look.
Does anyone know the character limit that should be used for pre-header so that it does not crop up on different email clients or devices, i reckon 30 to 35 works best?