Hello,

In current 3.5.x series, you can only order the custom fields (order depending of ordering in admin list of custom fields).

But, it will be possible with 3.6.0 (currently in beta version, tested by Pro Users) to order all the fields (custom fields and override fields, a new system to override a core field, and to allow ordering with custom fields).

So, in 3.6.0 coming in August (as soon as possible), you will have much more control on registration forms :
- ordering of all form fields
- Possibility to manage custom fields in groups, and so to have a custom form different for each event

And more to come with this important version 3.6.0!

Best Regards,
Cyril