Thank you for your patience with this.
Upon further review, we’re noting and realizing that the current version of the plugin is hardcoded to use the “custom field 1”, “custom field 2”, etc convention that is largely from the older Constant Contact API version that the plugin utilizes. Previously the fields weren’t customizable in name from my understanding
We’re in the works of getting the plugin to make use of the current API version, which is version 3, but I believe we’ll also need to get integration with custom names for custom fields capabilities added to the plugin as well. So at least for the moment, it’s not possible, with the WordPress Constant Contact Forms plugin. The forms that you can create from right in your Constant Contact account dashboard should be fully compatible though, and those should be easily placed wherever you can put custom markup in your website.