RE: Email preview text and AB test options in new release? Can't find.
Hi Graham,
It seems that there are some noticeable changes to the now form, such as Legal designation and Content type fields were merged with fields of Design tab;
Please open Designer form of Marketing Email in form editor to check whether the Preview Text field could be added to the form manually.(Because it is an existing field of Marketing Email entity.)
As for the AB testing options, it should be available in Designer > Design tab by default, try to create a new main form to Marketing Email to test if the option would appear again, if it couldn't be found in any tabs.
Regards,
Clofly