Pass custom fields as merge fields
Note: this functionality requires the purchase of the Custom Fields add-on too.
Added in version 1.1.0 of the MailChimp addon, you can now pass custom fields to your MailChimp lists.
Navigate to Users -> WPUM Settings -> Extensions -> MailChimp and scroll down the page, you'll notice a new "Send additional fields" table where you can configure your custom fields and merge fields.
Upon installation/update of the add-on, you must press the "Reload merge fields" button in order to load the merge fields of your list. For ease of use, the merge fields will be loaded from the first list that you have enabled.
Once merge fields have been loaded, press the "add new" button and configure the custom field and merge field that you want to match.
Once selected, press the "create new field" button to save the configuration. That's it.
Upon registration and account update, WPUM will send the fields to your MailChimp account.