How to Assign Custom Fields into Mini Registration
This feature was deprecated in EasySocial 2 in favor of workflows.
In EasySocial, you can assign custom fields into mini registration. This can be enabled or disabled from the back end settings of EasySocial under Joomla > Components > EasySocial > Profile Types > (Profile Type) > Custom Fields
Choose which custom field you want to assign into mini registration and click on edit button. Then click on the View tab. As you can see here there are a setting to enable custom field appear in mini registration.

